RESUMO
In the present study we evaluated the cardiovascular effects produced by microinjection of the new component of the renin-angiotensin system, alamandine, into caudal ventrolateral medulla of urethane-anesthetized normotensive and hypertensive 2K1C rats. The participation of different angiotensin receptors in the effects of alamandine was also evaluated. Microinjection of angiotensin-(1-7) was used for comparison. The microinjection of 4, 40 and 140pmol of alamandine or angiotensin-(1-7) into caudal ventrolateral medulla induced similar hypotensive effects in Sham-operated rats. However, contrasting with angiotensin-(1-7), in 2K1C rats the MAP response to the highest dose of alamandine was similar to that observed with saline. The microinjection of A-779, a selective Mas receptor antagonist, blunted the angiotensin-(1-7) effects but did not block the hypotensive effect of alamandine in Sham or in 2K1C rats. However, microinjection of D-Pro7-angiotensin-(1-7), a Mas/MrgD receptor antagonist, blocked the hypotensive effect induced by both peptides. Furthermore, microinjection of PD123319, a putative AT2 receptor antagonist blocked the hypotensive effect of alamandine, but not of angiotensin-(1-7), in Sham and 2K1C rats. Microinjection of the AT1 receptor antagonist, losartan, did not alter the hypotensive effect of angiotensin-(1-7) or alamandine in both groups. These results provide new insights about the differential mechanisms participating in the central cardiovascular effects of alamandine and angiotensin-(1-7) in normotensive and 2K1C hypertensive rats.
Assuntos
Bloqueadores do Receptor Tipo 2 de Angiotensina II/farmacologia , Angiotensina I/toxicidade , Hipertensão/induzido quimicamente , Oligopeptídeos/toxicidade , Fragmentos de Peptídeos/toxicidade , Animais , Imidazóis/farmacologia , Masculino , Piridinas/farmacologia , Ratos , Receptor Tipo 2 de Angiotensina/metabolismo , Sistema Renina-Angiotensina/efeitos dos fármacosRESUMO
Exercise training (Ex) has been recommended for its beneficial effects in hypertensive states. The present study evaluated the time-course effects of Ex without workload on mean arterial pressure (MAP), reflex bradycardia, cardiac and renal histology, and oxidative stress in two-kidney, one-clip (2K1C) hypertensive rats. Male Fischer rats (10 weeks old; 150–180 g) underwent surgery (2K1C or SHAM) and were subsequently divided into a sedentary (SED) group and Ex group (swimming 1 h/day, 5 days/week for 2, 4, 6, 8, or 10 weeks). Until week 4, Ex decreased MAP, increased reflex bradycardia, prevented concentric hypertrophy, reduced collagen deposition in the myocardium and kidneys, decreased the level of thiobarbituric acid-reactive substances (TBARS) in the left ventricle, and increased the catalase (CAT) activity in the left ventricle and both kidneys. From week 6 to week 10, however, MAP and reflex bradycardia in 2K1C Ex rats became similar to those in 2K1C SED rats. Ex effectively reduced heart rate and prevented collagen deposition in the heart and both kidneys up to week 10, and restored the level of TBARS in the left ventricle and clipped kidney and the CAT activity in both kidneys until week 8. Ex without workload for 10 weeks in 2K1C rats provided distinct beneficial effects. The early effects of Ex on cardiovascular function included reversing MAP and reflex bradycardia. The later effects of Ex included preventing structural alterations in the heart and kidney by decreasing oxidative stress and reducing injuries in these organs during hypertension.
Assuntos
Animais , Masculino , Hipertensão Renovascular/fisiopatologia , Rim/patologia , Miocárdio/patologia , Estresse Oxidativo/fisiologia , Condicionamento Físico Animal/fisiologia , Pressão Arterial/fisiologia , Barorreflexo/fisiologia , Bradicardia/metabolismo , Bradicardia/patologia , Catalase/metabolismo , Frequência Cardíaca/fisiologia , Rim/metabolismo , Miocárdio/enzimologia , Miocárdio/metabolismo , Artéria Renal/cirurgia , Comportamento Sedentário , Estruturas Criadas Cirurgicamente , Fatores de Tempo , Substâncias Reativas com Ácido Tiobarbitúrico/análiseRESUMO
Exercise training (Ex) has been recommended for its beneficial effects in hypertensive states. The present study evaluated the time-course effects of Ex without workload on mean arterial pressure (MAP), reflex bradycardia, cardiac and renal histology, and oxidative stress in two-kidney, one-clip (2K1C) hypertensive rats. Male Fischer rats (10 weeks old; 150-180 g) underwent surgery (2K1C or SHAM) and were subsequently divided into a sedentary (SED) group and Ex group (swimming 1 h/day, 5 days/week for 2, 4, 6, 8, or 10 weeks). Until week 4, Ex decreased MAP, increased reflex bradycardia, prevented concentric hypertrophy, reduced collagen deposition in the myocardium and kidneys, decreased the level of thiobarbituric acid-reactive substances (TBARS) in the left ventricle, and increased the catalase (CAT) activity in the left ventricle and both kidneys. From week 6 to week 10, however, MAP and reflex bradycardia in 2K1C Ex rats became similar to those in 2K1C SED rats. Ex effectively reduced heart rate and prevented collagen deposition in the heart and both kidneys up to week 10, and restored the level of TBARS in the left ventricle and clipped kidney and the CAT activity in both kidneys until week 8. Ex without workload for 10 weeks in 2K1C rats provided distinct beneficial effects. The early effects of Ex on cardiovascular function included reversing MAP and reflex bradycardia. The later effects of Ex included preventing structural alterations in the heart and kidney by decreasing oxidative stress and reducing injuries in these organs during hypertension.
Assuntos
Hipertensão Renovascular/fisiopatologia , Rim/patologia , Miocárdio/patologia , Estresse Oxidativo/fisiologia , Condicionamento Físico Animal/fisiologia , Animais , Pressão Arterial/fisiologia , Barorreflexo/fisiologia , Bradicardia/metabolismo , Bradicardia/patologia , Catalase/metabolismo , Frequência Cardíaca/fisiologia , Rim/metabolismo , Masculino , Miocárdio/enzimologia , Miocárdio/metabolismo , Ratos Endogâmicos F344 , Artéria Renal/cirurgia , Comportamento Sedentário , Estruturas Criadas Cirurgicamente , Substâncias Reativas com Ácido Tiobarbitúrico/análise , Fatores de TempoRESUMO
We hypothesize that exercise training (EX) reverses the level of nitric oxide (NO) and oxidative stress into rostral ventrolateral medulla (RVLM) of renovascular hypertensive rats (two kidneys, one clip - 2K1C). Microinjections of L-arginine (5 nmol), L-NAME (10 nmol), or saline (100 nl) were made into RVLM of 2K1C and normotensive (SHAM) rats sedentary (SED) or subjected to swimming for 4 weeks. mRNA expression (by qRT-PCR) of nitric oxide synthases isoforms (nNOS, eNOS, and iNOS), manganese superoxide dismutase (MnSOD), copper and zinc superoxide (Cu/ZnSOD), catalase (CAT), NADPH oxidase subunit p22(phox), concentration of thiobarbituric acid-reactive substances (TBARS), and CAT activity into RVLM were evaluated. The mean arterial pressure was reduced in 2K1C EX compared with that in 2K1C SED rats. L-arginine into RVLM induced hypertensive effect in 2K1C and SHAM SED rats, while L-NAME prevented hypertensive effect only in SHAM-SED. EX reduced hypertensive effect of L-arginine in SHAM and 2K1C rats. mRNA expression of NOS isoforms, p22(phox), and concentration of TBARS were increased while CAT and Cu/ZnSOD expression and CAT activity decreased into RVLM of 2K1C-SED compared with SHAM-SED rats. Additionally, EX reversed mRNA expression of CAT and NOS isoforms, concentration of TBARS, and CAT activity into RVLM of 2K1C-EX rats. These data suggest that the levels of NOS and oxidative stress into RVLM are important to determine the level of hypertension. Furthermore, EX can restore the blood pressure by reversing the levels of NOS and CAT expression, and reducing TBARS concentration into RVLM for the physiological state.
Assuntos
Hipertensão/metabolismo , Bulbo/fisiopatologia , Óxido Nítrico Sintase/metabolismo , Condicionamento Físico Animal/métodos , Animais , Masculino , Estresse Oxidativo/efeitos dos fármacos , RatosRESUMO
BACKGROUND AND PURPOSE: A long-term imbalance between pro- and anti-inflammatory mediators leads to airway remodelling, which is strongly correlated to most of the symptoms, severity and progression of chronic lung inflammation. The Angiotensin-(1-7) [Ang-(1-7)]/Mas receptor axis of the renin-angiotensin system is associated with attenuation of acute and chronic inflammatory processes. In this study, we investigated the effects of Ang-(1-7) treatment in a model of chronic allergic lung inflammation. EXPERIMENTAL APPROACH: Mice were sensitized to ovalbumin (OVA; 4 injections over 42 days, 14 days apart) and were challenged three times per week (days 21-46). These mice received Ang-(1-7) (1 µg·h(-1) , s.c.) by osmotic mini-pumps, for the last 28 days. Histology and morphometric analysis were performed in left lung and right ventricle. Airway responsiveness to methacholine, analysis of Ang-(1-7) levels (RIA), collagen I and III (qRT-PCR), ERK1/2 and JNK (Western blotting), IgE (elisa), cytokines and chemokines (elisa multiplex), and immunohistochemistry for Mas receptors were performed. KEY RESULTS: Infusion of Ang-(1-7) in OVA-sensitized and challenged mice decreased inflammatory cell infiltration and collagen deposition in the airways and lung parenchyma, and prevented bronchial hyperresponsiveness. These effects were accompanied by decreased IgE and ERK1/2 phosphorylation, and decreased pro-inflammatory cytokines. Mas receptors were detected in the epithelium and bronchial smooth muscle, suggesting a site in the lung for the beneficial actions of Ang-(1-7). CONCLUSIONS AND IMPLICATIONS: Ang-(1-7) exerted beneficial attenuation of three major features of chronic asthma: lung inflammation, airway remodelling and hyperresponsiveness. Our results support an important protective role of Ang-(1-7) in lung inflammation.
Assuntos
Remodelação das Vias Aéreas/efeitos dos fármacos , Angiotensina I/farmacologia , Anti-Inflamatórios/farmacologia , Hiper-Reatividade Brônquica/prevenção & controle , Broncoconstrição/efeitos dos fármacos , Pulmão/efeitos dos fármacos , Fragmentos de Peptídeos/farmacologia , Pneumonia/prevenção & controle , Hipersensibilidade Respiratória/prevenção & controle , Animais , Hiper-Reatividade Brônquica/induzido quimicamente , Hiper-Reatividade Brônquica/metabolismo , Hiper-Reatividade Brônquica/fisiopatologia , Colágeno/metabolismo , Citocinas/metabolismo , Modelos Animais de Doenças , Hipertrofia Ventricular Direita/induzido quimicamente , Hipertrofia Ventricular Direita/fisiopatologia , Hipertrofia Ventricular Direita/prevenção & controle , Imunoglobulina E/sangue , Mediadores da Inflamação/metabolismo , Pulmão/metabolismo , Pulmão/fisiopatologia , Masculino , Camundongos Endogâmicos BALB C , Proteína Quinase 1 Ativada por Mitógeno/metabolismo , Proteína Quinase 3 Ativada por Mitógeno/metabolismo , Ovalbumina , Fosforilação , Pneumonia/induzido quimicamente , Pneumonia/metabolismo , Pneumonia/fisiopatologia , Proto-Oncogene Mas , Proteínas Proto-Oncogênicas/agonistas , Proteínas Proto-Oncogênicas/metabolismo , Receptores Acoplados a Proteínas G/agonistas , Receptores Acoplados a Proteínas G/metabolismo , Hipersensibilidade Respiratória/induzido quimicamente , Hipersensibilidade Respiratória/metabolismo , Hipersensibilidade Respiratória/fisiopatologia , Transdução de Sinais/efeitos dos fármacosRESUMO
BACKGROUND AND PURPOSE: AVE 0991 (AVE) is a non-peptide compound, mimic of the angiotensin (Ang)-(1-7) actions in many tissues and pathophysiological states. Here, we have investigated the effect of AVE on pulmonary remodelling in a murine model of ovalbumin (OVA)-induced chronic allergic lung inflammation. EXPERIMENTAL APPROACH: We used BALB/c mice (6-8 weeks old) and induced chronic allergic lung inflammation by OVA sensitization (20 µg·mouse(-1) , i.p., four times, 14 days apart) and OVA challenge (1%, nebulised during 30 min, three times per·week, for 4 weeks). Control and AVE groups were given saline i.p and challenged with saline. AVE treatment (1 mg·kg(-1) ·per day, s.c.) or saline (100 µL·kg(-1) ·per day, s.c.) was given during the challenge period. Mice were anaesthetized 72 h after the last challenge and blood and lungs collected. In some animals, primary bronchi were isolated to test contractile responses. Cytokines were evaluated in bronchoalveolar lavage (BAL) and lung homogenates. KEY RESULTS: Treatment with AVE of OVA sensitised and challenged mice attenuated the altered contractile response to carbachol in bronchial rings and reversed the increased airway wall and pulmonary vasculature thickness and right ventricular hypertrophy. Furthermore, AVE reduced IL-5 and increased IL-10 levels in the BAL, accompanied by decreased Ang II levels in lungs. CONCLUSIONS AND IMPLICATIONS: AVE treatment prevented pulmonary remodelling, inflammation and right ventricular hypertrophy in OVA mice, suggesting that Ang-(1-7) receptor agonists are a new possibility for the treatment of pulmonary remodelling induced by chronic asthma.
Assuntos
Remodelação das Vias Aéreas/efeitos dos fármacos , Angiotensina I/farmacologia , Antiasmáticos/farmacologia , Asma/tratamento farmacológico , Imidazóis/farmacologia , Pulmão/efeitos dos fármacos , Fragmentos de Peptídeos/farmacologia , Artéria Pulmonar/efeitos dos fármacos , Veias Pulmonares/efeitos dos fármacos , Angiotensina II/metabolismo , Animais , Asma/induzido quimicamente , Asma/imunologia , Asma/metabolismo , Asma/fisiopatologia , Líquido da Lavagem Broncoalveolar/imunologia , Broncoconstrição/efeitos dos fármacos , Doença Crônica , Citocinas/metabolismo , Modelos Animais de Doenças , Hipertrofia Ventricular Direita/metabolismo , Hipertrofia Ventricular Direita/prevenção & controle , Pulmão/irrigação sanguínea , Pulmão/imunologia , Pulmão/metabolismo , Pulmão/fisiopatologia , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Mimetismo Molecular , Ovalbumina , Proto-Oncogene Mas , Proteínas Proto-Oncogênicas/efeitos dos fármacos , Proteínas Proto-Oncogênicas/metabolismo , Artéria Pulmonar/imunologia , Artéria Pulmonar/metabolismo , Artéria Pulmonar/fisiopatologia , Veias Pulmonares/imunologia , Veias Pulmonares/metabolismo , Veias Pulmonares/fisiopatologia , Receptores Acoplados a Proteínas G/efeitos dos fármacos , Receptores Acoplados a Proteínas G/metabolismo , Fatores de TempoRESUMO
We examined the effect of exercise training (Ex) without (Ex 0 percent) or with a 3 percent workload (Ex 3 percent) on different cardiac and renal parameters in renovascular hypertensive (2K1C) male Fisher rats weighing 150-200 g. Ex was performed for 5 weeks, 1 h/day, 5 days/week. Ex 0 percent or Ex 3 percent induced similar attenuation of baseline mean arterial pressure (MAP, 119 ± 5 mmHg in 2K1C Ex 0 percent, N = 6, and 118 ± 5 mmHg in 2K1C Ex 3 percent, N = 11, vs 99 ± 4 mmHg in sham sedentary (Sham Sed) controls, N = 10) and heart rate (HR, bpm) (383 ± 13 in 2K1C Ex 0 percent, N = 6, and 390 ± 14 in 2K1C Ex 3 percent, N = 11 vs 371 ± 11 in Sham Sed, N = 10,). Ex 0 percent, but not Ex 3 percent, improved baroreflex bradycardia (0.26 ± 0.06 ms/mmHg, N = 6, vs 0.09 ± 0.03 ms/mmHg in 2K1C Sed, N = 11). Morphometric evaluation suggested concentric left ventricle hypertrophy in sedentary 2K1C rats. Ex 0 percent prevented concentric cardiac hypertrophy, increased cardiomyocyte diameter and decreased cardiac vasculature thickness in 2K1C rats. In contrast, in 2K1C, Ex 3 percent reduced the concentric remodeling and prevented the increase in cardiac vasculature wall thickness, decreased the cardiomyocyte diameter and increased collagen deposition. Renal morphometric analysis showed that Ex 3 percent induced an increase in vasculature wall thickness and collagen deposition in the left kidney of 2K1C rats. These data suggest that Ex 0 percent has more beneficial effects than Ex 3 percent in renovascular hypertensive rats.
Assuntos
Animais , Masculino , Ratos , Coração/fisiopatologia , Hipertensão Renovascular/fisiopatologia , Rim/fisiopatologia , Condicionamento Físico Animal/fisiologia , Pressão Sanguínea/fisiologia , Peso Corporal/fisiologia , Bradicardia/fisiopatologia , Tamanho Celular , Frequência Cardíaca/fisiologia , Hipertrofia Ventricular Esquerda/prevenção & controle , Rim/patologia , Miocárdio/patologia , Miócitos Cardíacos/patologiaRESUMO
We examined the effect of exercise training (Ex) without (Ex 0%) or with a 3% workload (Ex 3%) on different cardiac and renal parameters in renovascular hypertensive (2K1C) male Fisher rats weighing 150-200 g. Ex was performed for 5 weeks, 1 h/day, 5 days/week. Ex 0% or Ex 3% induced similar attenuation of baseline mean arterial pressure (MAP, 119 ± 5 mmHg in 2K1C Ex 0%, N = 6, and 118 ± 5 mmHg in 2K1C Ex 3%, N = 11, vs 99 ± 4 mmHg in sham sedentary (Sham Sed) controls, N = 10) and heart rate (HR, bpm) (383 ± 13 in 2K1C Ex 0%, N = 6, and 390 ± 14 in 2K1C Ex 3%, N = 11 vs 371 ± 11 in Sham Sed, N = 10,). Ex 0%, but not Ex 3%, improved baroreflex bradycardia (0.26 ± 0.06 ms/mmHg, N = 6, vs 0.09 ± 0.03 ms/mmHg in 2K1C Sed, N = 11). Morphometric evaluation suggested concentric left ventricle hypertrophy in sedentary 2K1C rats. Ex 0% prevented concentric cardiac hypertrophy, increased cardiomyocyte diameter and decreased cardiac vasculature thickness in 2K1C rats. In contrast, in 2K1C, Ex 3% reduced the concentric remodeling and prevented the increase in cardiac vasculature wall thickness, decreased the cardiomyocyte diameter and increased collagen deposition. Renal morphometric analysis showed that Ex 3% induced an increase in vasculature wall thickness and collagen deposition in the left kidney of 2K1C rats. These data suggest that Ex 0% has more beneficial effects than Ex 3% in renovascular hypertensive rats.
Assuntos
Coração/fisiopatologia , Hipertensão Renovascular/fisiopatologia , Rim/fisiopatologia , Condicionamento Físico Animal/fisiologia , Animais , Pressão Sanguínea/fisiologia , Peso Corporal/fisiologia , Bradicardia/fisiopatologia , Tamanho Celular , Frequência Cardíaca/fisiologia , Hipertrofia Ventricular Esquerda/prevenção & controle , Rim/patologia , Masculino , Miocárdio/patologia , Miócitos Cardíacos/patologia , Ratos , Ratos Endogâmicos F344RESUMO
Neurons in the dorsomedial hypothalamus (DMH) play a key role in mediating tachycardia elicited by emotional stress. DMH activation by microinjections of the GABA(A) antagonist evokes tachycardia and physiological changes typically seen in experimental stress. DMH inhibition abolishes the tachycardia evoked by stress. Based on anatomic evidences for lateralization in the pathways from DMH, we investigated a possible inter-hemispheric difference in DMH-evoked cardiovascular responses. In anesthetized rats we compared changes in heart rate (HR), renal sympathetic activity (RSNA), mesenteric blood flow (MBF) and tail vascular conductance produced by activation of right (R) and left (L) sides of the DMH. We also evaluated the tachycardia produced by air jet stress after inhibition of R or L DMH. There were always greater increases in RSNA when bicuculline was injected ipsilaterally to the side where these parameters were recorded (average DeltaRSNA: L=+50% and R=+26%; P<0.05). Compared to pre-injection values, right DMH activation caused pronounced decrease (0.87+/-0.1% vs. 0.4+/-0.11%/mm Hg; P<0.05), whereas bicuculline methiodide (BMI) into left DMH produced no significant changes (0.95+/-0.09% vs. 1.04+/-0.25%/mm Hg) in tail vascular conductance. R or L DMH disinhibition produced decreases in MBF, but no differences in the range of these changes were observed. Activation of the right DMH caused greater tachycardia compared to the left DMH activation (average DeltaHR: R=+92 bpm; L=+48 bpm; P<0.05). Tachycardia evoked by air jet stress was smallest after right DMH inhibition (average DeltaHR: R=+57 bpm and L=+134 bpm; P<0.05). These results indicate that the descending cardiovascular pathways from DMH are predominantly lateralized and the right DMH might exert a prominent control on heart rate changes during emotional stress.
Assuntos
Vias Autônomas/fisiologia , Fenômenos Fisiológicos Cardiovasculares , Núcleo Hipotalâmico Dorsomedial/fisiologia , Vias Eferentes/fisiologia , Lateralidade Funcional/fisiologia , Animais , Vias Autônomas/citologia , Vias Autônomas/efeitos dos fármacos , Bicuculina/farmacologia , Núcleo Hipotalâmico Dorsomedial/citologia , Núcleo Hipotalâmico Dorsomedial/efeitos dos fármacos , Vias Eferentes/citologia , Vias Eferentes/efeitos dos fármacos , Antagonistas GABAérgicos/farmacologia , Frequência Cardíaca/fisiologia , Masculino , Ratos , Ratos Wistar , Fluxo Sanguíneo Regional/fisiologia , Circulação Esplâncnica/fisiologia , Estresse Psicológico/fisiopatologia , Fibras Simpáticas Pós-Ganglionares/anatomia & histologia , Fibras Simpáticas Pós-Ganglionares/fisiologia , Sistema Nervoso Simpático/anatomia & histologia , Sistema Nervoso Simpático/fisiologia , Taquicardia/fisiopatologiaRESUMO
In the present study, the effect of caudal ventrolateral medulla (CVLM) microinjection of angiotensin-(1-7) (Ang-(1-7)) and angiotensin II (Ang II) on mean arterial pressure (MAP), heart rate (HR) and pulsatile vascular blood flow (VBF; Transonic System) of the femoral, renal or mesenteric arteries was evaluated in male Wistar and spontaneously hypertensive rats (SHR) anesthetized with urethane. The vascular resistance (VR) was calculated by the ratio between the changes in MAP and VBF. Ang-(1-7) (40 ng) and Ang II (40 ng) microinjection into the CVLM caused similar depressor effects in Wistar rats and SHR. The hypotensive effect produced by Ang-(1-7) into the CVLM of Wistar rats was accompanied by a decrease in femoral (DeltaVR/VRbaseline=-0.12+/-0.04 vs. 0.001+/-0.03; after saline) and renal (DeltaVR/VRbaseline=-0.10+/-0.02 vs. -0.003+/-0.02; after saline) vascular resistance. On the other hand, the Ang II hypotensive effect in Wistar rats produced only changes in renal vascular resistance (DeltaVR/VRbaseline=-0.16+/-0.02 vs. -0.003+/-0.02; after saline). In SHR, the hypotensive effect produced by Ang-(1-7) and Ang II caused decrease in renal vascular resistance (DeltaVR/VRbaseline=-0.18+/-0.03 and -0.13+/-0.01, respectively, as compared with saline, DeltaVR/VRbaseline=-0.06+/-0.02), but did not alter the femoral or mesenteric vascular resistance. These data show that Ang II and Ang-(1-7) hypotensive effect at the CVLM involves the participation of different vascular beds. Further, the lack of involvement of the femoral vascular bed in SHR suggests that hypertension may induce alteration in the neural control of the different vascular beds, at least at the CVLM.
Assuntos
Angiotensina II/farmacologia , Angiotensina I/farmacologia , Anti-Hipertensivos/farmacologia , Hemodinâmica/efeitos dos fármacos , Bulbo/efeitos dos fármacos , Fragmentos de Peptídeos/farmacologia , Vasoconstritores/farmacologia , Análise de Variância , Animais , Pressão Sanguínea/efeitos dos fármacos , Frequência Cardíaca/efeitos dos fármacos , Masculino , Microinjeções/métodos , Ratos , Ratos Endogâmicos SHR , Ratos Wistar , Fluxo Sanguíneo Regional/efeitos dos fármacosRESUMO
In the present study, we evaluated the involvement of the rennin-angiotensin system (RAS) in the control of the blood pressure (BP), baroreceptor-mediated bradycardia and the reactivity of caudal ventrolateral medulla (CVLM) neurons to Ang II and to AT(2) receptor antagonist in sedentary or trained renovascular hypertensive rats. Physical activity did not significantly change the baseline mean arterial pressure (MAP), heart rate (HR) or the sensitivity of the baroreflex bradycardia in normotensive Sham rats. However, in 2K1C hypertensive rats, physical activity induced a significant fall in baseline MAP and HR and produced an improvement of the baroreflex function (bradycardic component). The microinjections of Ang II into the CVLM produced similar decreases in MAP in all groups, Sham and 2K1C, sedentary and trained rats. The hypotensive effect of Ang II at the CVLM was blocked by previous microinjection of the AT(2) receptors antagonist, PD123319, in all groups of rats. Unexpectedly, microinjection of PD123319 at the CVLM produced a depressor effect in 2K1C sedentary that was attenuated in 2K1C trained rats. No significant changes in MAP were observed after PD123319 in Sham rats, sedentary or trained. These data showed that low-intensity physical activity is effective in lowering blood pressure and restoring the sensitivity of the baroreflex bradycardia, however these cardiovascular effects are not accompanied by changes in the responsiveness to Ang II at CVLM in normotensive or hypertensive, 2K1C rats. In addition, the blood pressure changes observed after AT(2) blockade in 2K1C rats suggest that hypertension may trigger an imbalance of AT(1)/AT(2) receptors at the CVLM that may be restored, at least in part, by low-intensity physical activity.
Assuntos
Hipertensão Renovascular/fisiopatologia , Bulbo/fisiopatologia , Receptor Tipo 2 de Angiotensina/fisiologia , Angiotensina II/administração & dosagem , Angiotensina II/farmacologia , Bloqueadores do Receptor Tipo 2 de Angiotensina II , Animais , Barorreflexo/efeitos dos fármacos , Pressão Sanguínea/efeitos dos fármacos , Bradicardia/fisiopatologia , Frequência Cardíaca/efeitos dos fármacos , Imidazóis/administração & dosagem , Microinjeções , Neurônios/fisiologia , Condicionamento Físico Animal , Piridinas/administração & dosagem , Ratos , Ratos Endogâmicos SHR , Sistema Renina-Angiotensina , Sistema Nervoso Simpático/fisiopatologiaRESUMO
We have recently described, in the mouse aorta, the vasodilator effect of angiotensin-(1-7) (Ang-(1-7)) was mediated by activation of the Mas Ang-(1-7) receptor and that A-779 and D-Pro7-Ang-(1-7) act as Mas receptor antagonists. In this work we show pharmacological evidence for the existence of a different Ang-(1-7) receptor subtype mediating the vasodilator effect of Ang-(1-7) in the aorta from Sprague-Dawley (SD) rats. Ang-(1-7) induced an endothelium-dependent vasodilator effect in aortic rings from SD rats which was inhibited by removal of the endothelium and by L-NAME (100 microM) but not by indomethacin (10 microM). The Ang-(1-7) receptor antagonist D-Pro7-Ang-(1-7) (0.1 microM) abolished the vasodilator effect of the peptide. However, the other specific Ang-(1-7) receptor antagonist, A-779 in concentrations up to 10 microM, did not affect vasodilation induced by Ang-(1-7). The Ang II AT1 and AT2 receptors antagonists CV11974 (0.01 microM) and PD123319 (1 microM), respectively, the bradykinin B2 receptor antagonist HOE 140 (1 microM) and the inhibitor of ACE captopril (10 microM) did not change the effect of Ang-(1-7). Our results show that in the aorta of SD rats, the vasodilator effect of Ang-(1-7) is dependent on endothelium-derived nitric oxide. This effect is mediated by the activation of Ang-(1-7) receptors sensitive to D-Pro7-Ang-(1-7), but not to A-779, which suggests the existence of a different Ang-(1-7) receptor subtype.
Assuntos
Angiotensina I/metabolismo , Aorta Torácica/metabolismo , Fragmentos de Peptídeos/metabolismo , Receptores de Angiotensina/classificação , Receptores de Angiotensina/metabolismo , Angiotensina I/antagonistas & inibidores , Angiotensina I/farmacologia , Angiotensina II/análogos & derivados , Angiotensina II/farmacologia , Animais , Aorta Torácica/efeitos dos fármacos , Aorta Torácica/fisiologia , Técnicas In Vitro , Indometacina/farmacologia , Masculino , NG-Nitroarginina Metil Éster/farmacologia , Óxido Nítrico/metabolismo , Fragmentos de Peptídeos/antagonistas & inibidores , Fragmentos de Peptídeos/farmacologia , Ratos , Ratos Sprague-Dawley , Receptores de Angiotensina/efeitos dos fármacos , Vasodilatação/efeitos dos fármacosRESUMO
The objective of the present study was to determine the contribution of the autonomic nervous system and nitric oxide to the depressor effect produced by unilateral microinjection of ANG-(1-7) and ANG II into the caudal ventrolateral medulla (CVLM). Unilateral microinjection of ANG-(1-7), ANG II (40 pmol), or saline (100 nl) was made into the CVLM of male Wistar rats anesthetized with urethane before and after intravenous injection of 1) methyl-atropine, 2.5 mg/kg; 2) prazosin, 25 microg/kg; 3) the nitric oxide synthase (NOS) inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME), 5 mg/kg; or 4) the specific inhibitor of neuronal NOS, 7-nitroindazole (7-NI), 45 mg/kg. Arterial pressure and heart rate (HR) were continuously monitored. Microinjection of ANG-(1-7) or ANG II into the CVLM produced a significant decrease in mean arterial pressure (MAP; -11 +/- 1 mmHg, n = 12 and -10 +/- 1 mmHg, n = 10, respectively) that was not accompanied by consistent changes in HR or in cardiac output. The effect of ANG-(1-7) was abolished after treatment with methyl-atropine (-3 +/- 0.6 mmHg, n = 9) or L-NAME (-2.3 +/- 0.5 mmHg, n = 8) or 7-NI (-2.8 +/- 0.6 mmHg, n = 5). In contrast, these treatments did not significantly interfere with the ANG II effect (-10 +/- 2.6 mmHg, n = 8; -8 +/- 1.5 mmHg, n = 8; and -12 +/- 3.6 mmHg, n = 6; respectively). Peripheral treatment with prazosin abolished the hypotensive effect of ANG-(1-7) and ANG II. Microinjection of saline did not produce any significant change in MAP or in HR. These results suggest that the hypotensive effect produced by ANG II at the CVLM depends on changes in adrenergic vascular tonus and, more importantly, the hypotensive effect produced by ANG-(1-7) also involves a nitric oxide-related mechanism.
Assuntos
Angiotensina II/farmacologia , Angiotensina I/farmacologia , Pressão Sanguínea/efeitos dos fármacos , Bulbo/fisiologia , Fragmentos de Peptídeos/farmacologia , Antagonistas Adrenérgicos/farmacologia , Animais , Débito Cardíaco/efeitos dos fármacos , Antagonistas Colinérgicos/farmacologia , Depressão Química , Frequência Cardíaca/efeitos dos fármacos , Masculino , Microinjeções , Óxido Nítrico Sintase/antagonistas & inibidores , Óxido Nítrico Sintase Tipo I , Ratos , Ratos Wistar , Sistema Renina-Angiotensina/efeitos dos fármacos , Sistema Renina-Angiotensina/fisiologiaRESUMO
ACE inhibitors are extensively used in the treatment of hypertension mainly because of their efficiency in reducing blood pressure levels and decreasing vascular and cardiac hypertrophy. In addition, ACE inhibitors improve baroreceptor reflex control. Chronic inhibition of ACE produces (in addition to decreased angiotensin II levels) a severe increase in angiotensin-(1-7) [Ang-(1-7)] levels in several species. We have previously shown that Ang-(1-7) produces a facilitation of the baroreflex control of heart rate. In this study, we evaluated the participation of endogenous Ang-(1-7) in the improvement of baroreflex sensitivity in spontaneously hypertensive rats after central infusion of ramiprilat, an ACE inhibitor. Reflex changes in heart rate were elicited, in conscious rats, by bolus injections of phenylephrine (baroreflex bradycardia) before and after intracerebroventricular infusion of (1) saline (8 microL/h), 4 hours (n=5); (2) ramiprilat (14 microg/h), 4 hours (n=6); (3) ramiprilat for 2 hours, followed by ramiprilat combined with A-779 (4 microg/h), a selective Ang-(1-7) antagonist, for an additional 2 hours (n=6); and (4) A-779 for 2 hours, followed by A-779 combined with ramiprilat for an additional 2 hours (n=5). Intracerebroventricular infusion of ramiprilat produced an important increase ( approximately 40%) in baroreflex sensitivity (evaluated as the ratio between changes in heart rate and changes in mean arterial pressure) that was completely reversed by A-779. Furthermore, intracerebroventricular infusion of A-779 prevented the improvement of the baroreflex sensitivity produced by ramiprilat. Intracerebroventricular infusion of saline or A-779 alone did not significantly alter the baroreflex sensitivity. These results suggest that endogenous Ang-(1-7) is involved in the improvement of baroreflex sensitivity observed in spontaneously hypertensive rats during central ACE inhibition.
Assuntos
Inibidores da Enzima Conversora de Angiotensina/farmacologia , Barorreflexo/efeitos dos fármacos , Análise de Variância , Angiotensina I , Animais , Pressão Sanguínea/efeitos dos fármacos , Frequência Cardíaca/efeitos dos fármacos , Injeções Intraventriculares , Masculino , Fragmentos de Peptídeos , Ratos , Ratos Endogâmicos SHR , Sistema Renina-Angiotensina/efeitos dos fármacosRESUMO
We have previously demonstrated that microinjections of the selective angiotensin-(1-7) [ANG-(1-7)] antagonist, A-779, into the rostral ventrolateral medulla (RVLM) produces a significant fall in mean arterial pressure (MAP) and heart rate (HR) in both anesthetized and conscious rats. In contrast, microinjection of angiotensin II (ANG II) AT(1) receptor antagonists did not change MAP in anesthetized rats and produced dose-dependent increases in MAP when microinjected into the RVLM of conscious rats. In the present study, we evaluated whether endogenous ANG-(1-7) and ANG II acting at the RVLM contribute to the hypertension of transgenic rats harboring the mouse renin Ren-2 gene, TGR(mREN2)27. Unilateral microinjection of A-779 (0.1 nmol) produced a significant fall in MAP (-25 +/- 5 mmHg) and HR (-57 +/- 20 beats/min) of awake TGR rats. The hypotensive effect was greater than that observed in Sprague-Dawley (SD) rats (-9 +/- 2 mmHg). Microinjection of the AT(1) antagonist CV-11974 (0.2 nmol) produced a fall in MAP in TGR rats (-14 +/- 4 mmHg), contrasting with the pressor effect observed in SD rats (33 +/- 9 mmHg). These results indicate that endogenous ANG-(1-7) exerts a significant pressor action in the RVLM, contributing to the hypertension of TGR(mREN2)27 transgenic rats. The role of ANG II at the RVLM seems to be dependent on its endogenous level in this area.
Assuntos
Angiotensina II/análogos & derivados , Angiotensina II/metabolismo , Angiotensina I/metabolismo , Hipertensão/metabolismo , Bulbo/metabolismo , Fragmentos de Peptídeos/metabolismo , Renina/genética , Angiotensina I/administração & dosagem , Angiotensina II/administração & dosagem , Antagonistas de Receptores de Angiotensina , Animais , Animais Geneticamente Modificados , Anti-Hipertensivos/administração & dosagem , Benzimidazóis/administração & dosagem , Compostos de Bifenilo , Pressão Sanguínea/efeitos dos fármacos , Pressão Sanguínea/genética , Frequência Cardíaca/efeitos dos fármacos , Hipertensão/genética , Masculino , Bulbo/efeitos dos fármacos , Microinjeções , Fragmentos de Peptídeos/administração & dosagem , Ratos , Ratos Sprague-Dawley , Tetrazóis/administração & dosagemRESUMO
It has been shown that angiotensin-(1-7) (Ang-(1-7)) infusion potentiates the bradykinin (BK)-induced hypotensive response in conscious rats. The present study was conducted to identify Ang-(1-7)-BK interactions in the isolated rat heart perfused according to the Langendorff technique. Hearts were excised and perfused through the aortic stump under a constant flow with Krebs-Ringer solution and the changes in perfusion pressure and heart contractile force were recorded. Bolus injections of BK (2.5, 5, 10 and 20 ng) produced a dose-dependent hypotensive effect. Ang-(1-7) added to the perfusion solution (2 ng/ml) did not change the perfusion pressure or the contractile force but doubled the hypotensive effect of the lower doses of BK. The BK-potentiating Ang-(1-7) activity was blocked by pretreatment with indomethacin (5 mg/kg, ip) or L-NAME (30 mg/kg, ip). The Ang-(1-7) antagonist A-779 (50 ng/ml in Krebs-Ringer) completely blocked the effect of Ang-(1-7) on BK-induced vasodilation. These data suggest that the potentiation of the BK-induced vasodilation by Ang-(1-7) can be attributed to the release of nitric oxide and vasodilator prostaglandins through an Ang-(1-7) receptor-mediated mechanism.
Assuntos
Angiotensina I/farmacologia , Bradicinina/farmacologia , Vasos Coronários/efeitos dos fármacos , Fragmentos de Peptídeos/farmacologia , Vasodilatadores/farmacologia , Análise de Variância , Animais , Fármacos Cardiovasculares/farmacologia , Sinergismo Farmacológico , Inibidores Enzimáticos/farmacologia , Indometacina/farmacologia , Masculino , NG-Nitroarginina Metil Éster/farmacologia , Óxido Nítrico/fisiologia , Ratos , Ratos WistarRESUMO
It has been shown that angiotensin-(1-7) (Ang-(1-7)) infusion potentiates the bradykinin (BK)-induced hypotensive response in conscious rats. The present study was conducted to identify Ang-(1-7)-BK interactions in the isolated rat heart perfused according to the Langendorff technique. Hearts were excised and perfused through the aortic stump under a constant flow with Krebs-Ringer solution and the changes in perfusion pressure and heart contractile force were recorded. Bolus injections of BK (2.5, 5, 10 and 20 ng) produced a dose-dependent hypotensive effect. Ang-(1-7) added to the perfusion solution (2 ng/ml) did not change the perfusion pressure or the contractile force but doubled the hypotensive effect of the lower doses of BK. The BK-potentiating Ang-(1-7) activity was blocked by pretreatment with indomethacin (5 mg/kg, ip) or L-NAME (30 mg/kg, ip). The Ang-(1-7) antagonist A-779 (50 ng/ml in Krebs-Ringer) completely blocked the effect of Ang-(1-7) on BK-induced vasodilation. These data suggest that the potentiation of the BK-induced vasodilation by Ang-(1-7) can be attributed to the release of nitric oxide and vasodilator prostaglandins through an Ang-(1-7) receptor-mediated mechanism.
Assuntos
Animais , Masculino , Ratos , Angiotensina I/farmacologia , Bradicinina/farmacologia , Vasos Coronários/efeitos dos fármacos , Vasodilatadores/farmacologia , Análise de Variância , Fármacos Cardiovasculares/farmacologia , Inibidores Enzimáticos/farmacologia , Hipotensão , Indometacina/farmacologia , NG-Nitroarginina Metil Éster/farmacologia , Óxido Nítrico , Ratos WistarRESUMO
OBJECTIVES: In the present study, we evaluated the effect of angiotensin-(1-7) [Ang-(1-7)] and its selective antagonist, D-Ala7-Ang-(1-7) (A-779), at the nucleus tractus solitarii (nTS), in the modulation of the bradycardic component of the baroreceptor reflex. METHODS: Mean arterial pressure (MAP) and heart rate were continuously recorded. Reflex changes in heart rate elicited by bolus injection of graded doses of phenylephrine were evaluated before and after bilateral microinjection (glass micropipette) of Ang-(1-7) (10 pmol or 25 pmol), A-779 (50 pmol) or saline (vehicle) into the nTS of urethane anesthetized male Wistar rats or spontaneously hypertensive rats (SHR). The averaged ratio between reflex changes in heart rate and changes in MAP was used as index of baroreflex sensitivity. RESULTS: Microinjection of Ang-(1-7) into the nTS elicited significant decreases in MAP and heart rate in both Wistar and SHR. While the decrease in MAP was similar in both strains, the changes in heart rate were smaller in SHR. A-779 produced small changes in MAP and heart rate that were no different from those induced by saline. After microinjection of 10 pmol of Ang-(1-7) into the nTS of normotensive rats, there was a significant increase in baroreflex sensitivity. In SHR, only the microinjection of a higher dose (25 pmol) of Ang-(1-7) produced a significant increase in baroreflex sensitivity. A significant reduction inbaroreflex sensitivity was observed after microinjection of A-779 (50 pmol) in both strains. CONCLUSIONS: These results indicate that Ang-(1-7) exerts a tonic modulatory effect on the baroreflex control of heart rate at the nTS, probably through a non-AT1 non-AT2 receptor subtype. In addition, our data showed a reduced sensitivity to Ang-(1-7) at the nTS of SHR, that could be accounting, at least in part, for the decreased baroreflex sensitivity present in this model of hypertension.
Assuntos
Angiotensina II/análogos & derivados , Angiotensina I/farmacologia , Barorreflexo/efeitos dos fármacos , Barorreflexo/fisiologia , Frequência Cardíaca/efeitos dos fármacos , Frequência Cardíaca/fisiologia , Hipertensão/fisiopatologia , Fragmentos de Peptídeos/farmacologia , Núcleo Solitário/efeitos dos fármacos , Núcleo Solitário/fisiologia , Angiotensina I/administração & dosagem , Angiotensina I/antagonistas & inibidores , Angiotensina II/farmacologia , Animais , Pressão Sanguínea/efeitos dos fármacos , Pressão Sanguínea/fisiologia , Masculino , Microinjeções , Fragmentos de Peptídeos/administração & dosagem , Fragmentos de Peptídeos/antagonistas & inibidores , Ratos , Ratos Endogâmicos SHR , Ratos Wistar , Receptores de Angiotensina/efeitos dos fármacos , Núcleo Solitário/anatomia & histologiaRESUMO
In this study, we evaluated the bradykinin potentiating activity and ACE inhibitory activity of several Ang-(1-7)-related peptides: Ang-(2-7), Ang-(3-7), Ang-(4-7), Ang-(1-6), Ang-(1-5) and the selective antagonist of Ang-(1-7): D-[Ala7]Ang-(1-7) (A-779). In vivo experiments were performed in freely moving Wistar rats. ACE activity was evaluated by a fluorometric assay in rat plasma using Hip-His-Leu as a substrate. Intravenous injections of Ang-(1-7) (2.2 nmol) transformed the effect of a single dose of bradykinin (1 nmol) into the effect produced by a double dose. A similar bradykinin potentiating activity was demonstrated for Ang-(2-7) and Ang-(3-7). On the other hand, Ang-(1-5), Ang-(1-6), Ang-(4-7) and A-779 did not change the hypotensive effect of bradykinin in doses ranging from 8 up to 25 nmols. The hypotensive effect of bradykinin was increased by intravenous infusion (0.3 ng/min) of Ang-(1-7) > Ang-(2-7) > Ang-(3-7). Conversely, Ang-(1-5), Ang-(1-6), Ang-(4-7) or A-779 did not change the hypotensive effect of bradykinin. ACE inhibition with Ang-(1-7) related peptides occurred in the order: Ang-(2-7) > or = Ang-(3-7) > Ang-(1-7) [>>] Ang-(1-5) > Ang-(4-7) > or = Ang-(1-6) > or = A-779. A-779 in concentrations up to 10(-5) M did not change the ACE inhibitory activity of Ang-(1-7). These results suggest that Ang-(1-7), Ang-(2-7) and Ang-(3-7) can modulate bradykinin actions in vivo. More important, our data pointed out that alternative mechanisms besides interaction with ACE are required to explain the bradykinin potentiating activity of Ang-(1-7).
Assuntos
Angiotensina I/química , Angiotensina I/farmacologia , Inibidores da Enzima Conversora de Angiotensina/farmacologia , Anti-Hipertensivos/farmacologia , Bradicinina/farmacologia , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/farmacologia , Animais , Pressão Sanguínea/efeitos dos fármacos , Sinergismo Farmacológico , Infusões Intravenosas , Injeções Intravenosas , Masculino , Peptidil Dipeptidase A/sangue , Ratos , Ratos Wistar , VigíliaRESUMO
OBJECTIVE: To evaluate the effects of angiotensins acting at the rostral ventrolateral medulla (RVLM) on the cardiovascular adjustments following haemorrhage. DESIGN: Changes in mean arterial pressure (MAP) and heart rate (HR) produced by micro-injections of angiotensin II (Ang II) and angiotensin (Ang)-(1-7) and different angiotensin antagonists into the RVLM of anaesthetized rats submitted to haemorrhage, were determined. METHODS: Experiments were performed in 79 urethane-anaesthetized male Wistar rats. Ang-(1-7) (2.5 and 25 pmol), Ang II (25 pmol), [Sar1,Thr8]-Ang II (non-selective angiotensin antagonist, 0.2 nmol), A-779 (Ang-(1-7) antagonist, 0.1 nmol), losartan (AT1 Ang II receptor antagonist, 0.2 nmol) or vehicle (200 nl) were bilaterally micro-injected into the RVLM under basal conditions or 30 min after blood withdrawal (0.6 ml/100 g bodyweight). In additional groups, [Sar1,Thr8]-Ang II, A-779, losartan or vehicle were micro-injected into the RVLM 10 min before bleeding to uncover a possible role of endogenous peptides during haemorrhage. RESULTS: The pressor effect produced by Ang II micro-injection was not altered by haemorrhage. Conversely, haemorrhage significantly increased the magnitude and duration of the pressor effect of Ang-(1-7) at the RVLM. The fall in MAP induced by haemorrhage was similar after micro-injection of vehicle or A-779. However, micro-injection of [Sar1,Thr8]-Ang II significantly reduced the fall in MAP after haemorrhage. A similar finding was obtained with micro-injection of losartan. In addition, while RVLM micro-injection of [Sar1,Thr8]-Ang II or losartan 30 min after blood withdrawn produced MAP changes that were similar to that observed in control animals, micro-injection of A-779 did not significantly alter baseline MAP. CONCLUSIONS: These results suggest that changes in the RVLM reactivity to Ang-(1-7) but not Ang II may contribute to the haemodynamic adjustments triggered by acute reductions in blood volume. The data obtained with [Sar1,Thr8]-Ang II and losartan suggest a primary inhibitory role for endogenous Ang II at the RVLM during haemorrhage.