RESUMO
The stress experienced during rape seems to facilitate ovulation since the pregnancy rate in raped women is higher than that resulting from consensual intercourse. Adrenal progesterone, as well as central norepinephrine, is released in stressful situations. At adequate estrogenic levels, one of the main actions of progesterone is to anticipate the preovulatory LH surge through noradrenaline release. We aimed to investigate whether acute stresses that mimic those of rape (exposure to predator, restraint and cervix stimulation) applied on the proestrus morning in female rats could release progesterone, activate the noradrenergic neurons and facilitate the occurrence of the LH surge. Female rats were submitted to jugular vein cannulation immediately following acute stress: restraint (R), exposure to cat (P), uterine cervix stimulation (CS) applied individually or in association (SA). Non-stressed rats were used as control. Blood samples were collected from 11:00-18:00 h for LH, progesterone, corticosterone and estradiol measurements. Double labeling for c-Fos and tyrosine hydroxylase (TH) was examined in A1, A2 and A6 noradrenergic neurons after stresses. The SA group showed a greater stress-induced increase in progesterone compared to the other groups and the preovulatory LH surge was anticipated and amplified. This effect of SA seems to be related to the higher number of c-Fos/TH + neurons in the A1 and A2. The effect of anticipating the preovulatory surge of LH could in part elucidate why, in raped women, conception can occur in phases of the menstrual cycle other than the ovulatory phase facilitating the occurrence of pregnancies.
Assuntos
Neurônios Adrenérgicos , Progesterona , Animais , Estradiol/farmacologia , Feminino , Humanos , Hormônio Luteinizante , Norepinefrina , Ovulação , Gravidez , Progesterona/farmacologia , Ratos , Tirosina 3-Mono-OxigenaseRESUMO
The use of probiotics to prevent or treat mucosal inflammation has been studied; however, the combined effect of probiotics and prebiotics is unclear. The aim of this study was to test whether oral administration of a synbiotic (Simbioflora®) preparation containing Lactobacillus paracasei, Lactobacillus rhamnosus, Lactobacillus acidophilus and Bifidobacterium lactis plus fructooligosaccharide could help control mucosal inflammation in experimental mucositis induced by 5-fluorouracil (5-FU). Male BALB/c mice were randomly divided into six groups: control (CTL), control + prebiotic (CTL+P), control + synbiotic (CTL+S), mucositis (MUC), mucositis + prebiotic (MUC+P), and mucositis + synbiotic (MUC+S). Mice from the CTL+S, MUC+S, CTL+P, and MUC+P groups received synbiotic or prebiotic daily by oral gavage for 13 days. Mice in the CTL and MUC groups received the same volume of saline. On day 11, mice in the MUC, MUC+P, and MUC+S groups received an intraperitoneal injection of 300 mg/kg 5-FU to induce mucositis. After 72 h, all mice were euthanised. Intestinal permeability, intestinal histology, and biochemical parameters were analysed. Group MUC showed a greater weight loss and increased intestinal permeability (0.020 counts per min [cpm]/g) compared to the CTL group (0.01 cpm/g) P<0.05. Both treatments attenuated weight loss compared to the MUC group. Nonetheless, the synbiotic caused a greater reduction in intestinal permeability (0.012 cpm/g) compared to the MUC (0.020 cpm/g) and MUC+P (0.016 cpm/g) groups P<0.05. Mice in groups MUC+P and MUC+S displayed significant recovery of lesions and maintenance of the mucus layer. There were no differences in the short-chain fatty acid concentrations in the faeces between the MUC and CTL groups (P>0.05). Increased acetate and propionate concentrations were evidenced in the faeces of the MUC+P and MUC+S groups. Only the synbiotic treatment increased the butyrate concentration (P<0.05). The results indicate that administration of synbiotic can decrease mucosal damage caused by mucositis.
Assuntos
Mucosite/prevenção & controle , Simbióticos/administração & dosagem , Administração Oral , Animais , Bifidobacterium animalis/crescimento & desenvolvimento , Bifidobacterium animalis/metabolismo , Peso Corporal , Ácidos Graxos Voláteis/análise , Fezes/química , Fluoruracila/administração & dosagem , Fluoruracila/toxicidade , Trato Gastrointestinal/patologia , Lactobacillus/crescimento & desenvolvimento , Lactobacillus/metabolismo , Camundongos Endogâmicos BALB C , Mucosite/induzido quimicamente , Oligossacarídeos/administração & dosagem , Oligossacarídeos/metabolismo , Resultado do TratamentoRESUMO
Vaccinia virus (VACV) is an important pathogen. Although studies have shown relationships between probiotics and viruses, the effect of probiotics on VACV infection is unknown. Therefore, this work aims to investigate the probiotics effects on VACV infection. Mice were divided into four groups, two non-infected groups, one receiving the probiotic, the other one not receiving it, and two groups infected intranasally with VACV Western Reserve (VACV-WR) receiving or not receiving the probiotic. Viral titres in organs and cytokine production in the lungs were analysed. Lung samples were also subjected to histological analysis. The intake of probiotic results in reduction in viral spread with a significant decrease of VACV titer on lung, liver and brain of treated group. In addition,treatment with the probiotic results in attenuated mice lung inflammation showing fewer lesions on histological findings and decreased lethality in mice infected with VACV. The ingestion of Lactobacillus paracasei ST11 (LPST11) after VACV infection resulted in 2/9 animal lethality compared with 4/9 in the VACV group. This is the first study on probiotics and VACV interactions, providing not only information about this interaction, but also proposing a model for future studies involving probiotics and other poxvirus.
Assuntos
Lacticaseibacillus paracasei/fisiologia , Probióticos , Vaccinia virus/fisiologia , Vacínia/terapia , Animais , Citocinas/análise , Modelos Animais de Doenças , Ingestão de Alimentos , Inflamação/terapia , Pulmão/patologia , Pulmão/virologia , Masculino , Camundongos , Camundongos Endogâmicos BALB CRESUMO
The locus coeruleus (LC) has been suggested as a CO2 chemoreceptor site in mammals. Most of the studies involving the role of the LC in hypercapnic ventilatory responses have been performed in males. Since ovarian steroids modulate the activity of LC neurons and females have a different respiratory response to CO2 than males, we evaluated the activity of LC noradrenergic neurons during normocapnia and hypercapnia in female and male rats with distinct sex hormone levels. Ovariectomized (OVX), estradiol (E2)-treated ovariectomized (OVX+E2) and female rats on the diestrous day of the estrous cycle were evaluated. Concurrently, males were investigated as gonad-intact, orchidectomized (ORX), testosterone (T)-treated ORX (ORX+T), and E2-treated ORX (ORX+E2). Activation of LC neurons was determined by double-label immunohistochemistry to c-Fos and tyrosine hydroxylase (TH). Hypercapnia induced by 7% CO2 increased the number of c-Fos/TH-immunoreactive (ir) neurons in the LC of all groups when compared to air exposure. Hypercapnia-induced c-Fos expression did not differ between diestrous females and intact male rats. In the OVX+E2 group, there was attenuation in the c-Fos expression during normocapnia compared with OVX rats, but CO2 responsiveness was not altered. Moreover, in ORX rats, neither T nor E2 treatments changed c-Fos expression in LC noradrenergic neurons. Thus, in female rats, E2 reduces activation of LC noradrenergic neurons, whereas in males, sex hormones do not influence the LC activity.
Assuntos
Hormônios Esteroides Gonadais/metabolismo , Hipercapnia/fisiopatologia , Locus Cerúleo/fisiologia , Caracteres Sexuais , Ar , Animais , Dióxido de Carbono/administração & dosagem , Dióxido de Carbono/metabolismo , Castração , Modelos Animais de Doenças , Feminino , Hormônios Esteroides Gonadais/administração & dosagem , Imuno-Histoquímica , Masculino , Neurônios/fisiologia , Proteínas Proto-Oncogênicas c-fos/metabolismo , Ratos Wistar , Tirosina 3-Mono-Oxigenase/metabolismoRESUMO
Prolactin (PRL) secretion is inhibited by hypothalamic dopamine. Kisspeptin controls luteinising hormone (LH) secretion and is also involved in PRL regulation. We further investigated the effect of kisspeptin-10 (Kp-10) on the activity of tuberoinfundibular dopaminergic (TIDA) neurones and the role of oestradiol (E2 ) in this mechanism. Female and male rats were injected with i.c.v. Kp-10 and evaluated for PRL release and the activity of dopamine terminals in the median eminence (ME) and neurointermediate lobe of the pituitary (NIL). Kp-10 at the doses of 0.6 and 3 nmol increased plasma PRL and decreased 4-dihydroxyphenylacetic acid (DOPAC) levels in the ME and NIL of ovariectomised (OVX), E2 -treated rats but had no effect in OVX. In gonad-intact males, 3 nmol Kp-10 increased PRL secretion and decreased DOPAC levels in the ME but not in the NIL. Castrated males treated with either testosterone or E2 also displayed increased PRL secretion and reduced ME DOPAC in response to Kp-10, whereas castrated rats receiving oil or dihydrotestosterone were unresponsive. By contrast, the LH response to Kp-10 was not E2 -dependent in either females or males. Additionally, immunohistochemical double-labelling demonstrated that TIDA neurones of male rats contain oestrogen receptor (ER)-α, with a higher proportion of neurones expressing ERα than in dioestrous females. The dopaminergic neurones of periventricular hypothalamic nucleus displayed much lower ERα expression. Thus, TIDA neurones express ERα in male and female rats, and kisspeptin increases PRL secretion through inhibition of TIDA neurones in an E2 -dependent manner in both sexes. These findings provide new evidence about the role of kisspeptin in the regulation of dopamine and PRL.
Assuntos
Núcleo Arqueado do Hipotálamo/metabolismo , Neurônios Dopaminérgicos/metabolismo , Estradiol/metabolismo , Kisspeptinas/fisiologia , Prolactina/metabolismo , Animais , Feminino , Hormônio Luteinizante/metabolismo , Masculino , RatosRESUMO
Perimenopause, a transition period that precedes menopause, is characterized by neuroendocrine, metabolic and behavioral changes, and is associated with increased vulnerability to affective disorders. The decrease in ovarian follicles during perimenopause contributes to a dynamic and complex hormonal milieu that is not yet well characterized. In rodents, 4-vinylcyclohexene diepoxide (VCD) induces a gradual depletion of ovarian follicles, modeling the transition to menopause in women. This study was aimed to investigate, in VCD-treated rats, the hormonal status and the behavior in the elevated plus-maze (EPM), a widely used test to assess anxiety-like behavior. From the postnatal day 28, rats were treated with VCD or vehicle for 15 days. At 80±5 days after the beginning of treatment the experiments were performed at proestrus and diestrus. In the first experiment rats were decapitated, ovary was collected and blood samples were taken for estradiol, progesterone, follicle stimulant hormone (FSH), testosterone, dihydrotestosterone (DHT) and corticosterone measurements. In the second experiment, rats were subjected to the EPM for 5 min, and behavioral categories recorded. Administration of VCD induced follicular depletion as well as an increase of the number of atretic follicles demonstrating the treatment efficacy. The transitional follicular depletion was accompanied by lower progesterone, testosterone and DHT with no changes in the FSH, estradiol and corticosterone plasma levels. On the EPM, rats showed decreased open arm exploration and increased risk assessment behavior, indicating increased anxiety. These findings show that administration of VCD to induce ovarian failure results in endocrine and anxiety-related changes that are similar to the symptoms exhibited by women during menopause transition. Thus, this model seems to be promising in the study of perimenopause-related changes.
Assuntos
Ansiedade/induzido quimicamente , Cicloexenos/toxicidade , Folículo Ovariano/efeitos dos fármacos , Perimenopausa/efeitos dos fármacos , Perimenopausa/psicologia , Compostos de Vinila/toxicidade , Animais , Ansiedade/sangue , Corticosterona/sangue , Di-Hidrotestosterona/sangue , Modelos Animais de Doenças , Estradiol/sangue , Ciclo Estral/sangue , Feminino , Hormônio Foliculoestimulante/sangue , Aprendizagem em Labirinto/efeitos dos fármacos , Perimenopausa/sangue , Insuficiência Ovariana Primária/induzido quimicamente , Progesterona/sangue , Ratos , Testosterona/sangueRESUMO
Adrenal progesterone secretion increases along with corticosterone in response to stress in male and female rats to modulate some stress responses. Here we investigated the role of sex steroids in sex differences in the progesterone response to 60 min of restraint stress in adult male and female rats. Comparisons between males and females in the progesterone response were evaluated in parallel with corticosterone responses. From day 5 to 7 after gonadectomy, female and male rats were treated with estradiol or testosterone, respectively (OVX-E and ORCH-T groups), or oil (OVX and ORCH groups). Female rats in proestrus, intact and 7 d adrenalectomized (ADX) male rats were also studied. At 10:00 h, blood samples were withdrawn via an implanted jugular cannula before (-5 min), during (15, 30, 45, 60 min) and after (90 and 120 min) restraint stress to measure plasma progesterone and corticosterone concentrations by radioimmunoassay. Intact male and proestrus female rats exhibited similar progesterone responses to stress. Gonadectomy did not alter the amount of progesterone secreted during stress in female rats but decreased secretion in male rats. Unlike corticosterone, the progesterone response to stress in females was not influenced by estradiol. In males, testosterone replacement attenuated the progesterone and corticosterone responses to stress. Basal secretion of progesterone among intact, ORCH and ADX males was similar, but ADX-stressed rats secreted little progesterone. Hence, the gonads differently modulate adrenal progesterone and corticosterone responses to stress in female and male rats. The ovaries enhance corticosterone but not progesterone secretion, while the testes stimulate progesterone but not corticosterone secretion.
Assuntos
Corticosterona/metabolismo , Estradiol/farmacologia , Progesterona/metabolismo , Restrição Física/psicologia , Estresse Psicológico , Testosterona/farmacologia , Adrenalectomia , Animais , Feminino , Masculino , Orquiectomia , Ovariectomia , Ovário/fisiologia , Proestro , Ratos , Ratos Wistar , Caracteres Sexuais , Testículo/fisiologiaRESUMO
Cold stress-induced ovarian sympathetic activation is associated with the development of ovarian cysts in rats. Although we have hypothesised that polycystic ovary (PCO) features induced by cold stress, as prevented by lesion of the noradrenergic nucleus locus coeruleus (LC), were a result of the increased activity of the ovarian norepinephrine (NE) system, this was not evident after 8 weeks of stress. In the present study, we investigated the temporal changes in LC and ovarian NE activities and steroid secretion in rats exposed to single (SS) or repeated (RS) cold stress. SS and 4 week (4W)-RS but not 8 week (8W)-RS increased c-Fos expression in the LC and ovarian NE release. Plasma oestradiol, testosterone and progesterone levels tended to increase in 4W-RS and were elevated in 8W-RS rats, which displayed PCO morphology. ß-adrenergic receptor agonist increased steroid hormone release from the ovary of unstressed (US) but not from 8W-RS rats. To determine whether increased activity of noradrenergic system during the initial 4 weeks of RS would be sufficient to promote PCO, rats were exposed to 4 weeks of cold stress and kept in ambient temperature for the next 4 weeks (4W-RS/4W-US). Accordingly, PCO morphology, increased steroid secretion and decreased ovulation rate were found in 4W-RS/4W-US rats, strengthening the hypothesis that the initial increase in NE release triggers the development of PCO. The correlated activity of LC neurones and ovarian noradrenergic terminals and the induction of PCO in 4W-RS/4W-US rats provide functional evidence for a major role of NE in disrupting follicular development and causing the long-lasting endocrine abnormalities found in stress-induced PCO.
Assuntos
Temperatura Baixa/efeitos adversos , Locus Cerúleo/metabolismo , Norepinefrina/metabolismo , Ovário/metabolismo , Síndrome do Ovário Policístico/metabolismo , Estresse Fisiológico/fisiologia , Animais , Estradiol/sangue , Feminino , Locus Cerúleo/fisiopatologia , Neurônios/metabolismo , Ovário/fisiopatologia , Síndrome do Ovário Policístico/etiologia , Síndrome do Ovário Policístico/fisiopatologia , Progesterona/sangue , Ratos , Ratos Wistar , Sistema Nervoso Simpático/metabolismo , Sistema Nervoso Simpático/fisiopatologia , Testosterona/sangueRESUMO
Introduction: According to morphology, acromion can be classified into three types: I (flat), II (curved),and III (hooked) and its characteristics are related to age and rotator cuff pathology. Here we haveanalyzed acromion ́s morphology in scapulas of Brazilian human skeleton and tried to establish possiblemorphofunctional correlations to literature data.Materials and Methods:Fifty-seven scapulas from HumanAnatomy laboratories of Universidade Federal de Minas Gerais were selected and divided in groups accordingto acromion ́s tip morphology and angle.Results:We observed that distribution of acromial morphologywas 5,2% type I (flat), 57,9% type II (curved), 36,9% type III (hooked).Conclusion:Our data is importantto compare Brazilian scapula bones to those from various other regions or races and could contribute todemographic studies of shoulder disease probability in Brazilian population.
Assuntos
Humanos , Acrômio/anatomia & histologia , Brasil , Escápula/anatomia & histologia , Grupos PopulacionaisRESUMO
Empirical studies using visual search methods to investigate spider communities were conducted with different sampling protocols, including a variety of plot sizes, sampling efforts, and diurnal periods for sampling. We sampled 11 plots ranging in size from 5 by 10 m to 5 by 60 m. In each plot, we computed the total number of species detected every 10 min during 1 hr during the daytime and during the nighttime (0630 hours to 1100 hours, both a.m. and p.m.). We measured the influence of time effort on the measurement of species richness by comparing the curves produced by sample-based rarefaction and species richness estimation (first-order jackknife). We used a general linear model with repeated measures to assess whether the phase of the day during which sampling occurred and the differences in the plot lengths influenced the number of species observed and the number of species estimated. To measure the differences in species composition between the phases of the day, we used a multiresponse permutation procedure and a graphical representation based on nonmetric multidimensional scaling. After 50 min of sampling, we noted a decreased rate of species accumulation and a tendency of the estimated richness curves to reach an asymptote. We did not detect an effect of plot size on the number of species sampled. However, differences in observed species richness and species composition were found between phases of the day. Based on these results, we propose guidelines for visual search for tropical web spiders.
Assuntos
Biodiversidade , Aranhas/fisiologia , Animais , Entomologia/métodos , Modelos Lineares , Densidade Demográfica , Fatores de Tempo , Clima TropicalRESUMO
A secretory surge of prolactin occurs on the afternoon of oestrus in cycling rats. Pituitary prolactin is inhibited by dopamine. We evaluated the activity of the neuroendocrine dopaminergic neurones during oestrus and dioestrus, as determined by dopaminergic activity in the median eminence and neurointermediate lobe of the pituitary, as well as Fos-related antigen expression in tyrosine hydroxylase (TH)-immunoreactive (ir) neurones of the arcuate nucleus (ARC) and periventricular nucleus (Pe). During oestrus, the 4-dihydroxyphenylacetic acid/dopamine ratio in the median eminence decreased at 16.00 h, coinciding with the increase in plasma prolactin levels. Similarly, the expression of Fos-related antigen in TH-ir neurones of Pe and rostral-, dorsomedial- and caudal-ARC also decreased at 16.00 h. On dioestrus, 4-dihydroxyphenylacetic acid/dopamine ratio in the median eminence and Fos-related antigen expression in TH-ir neurones of Pe and rostral-ARC decreased at 18.00 h, whereas prolactin levels were unaltered. No variation in dopaminergic activity was found in the neurointermediate lobe of the pituitary on either oestrus or dioestrus. The number of TH-ir neurones in the ARC and parameters of dopaminergic activity were found to be generally lower on oestrus compared to dioestrus. The transitory decrease in the activity of neuroendocrine dopaminergic neurones temporally associated with the prolactin surge on the afternoon of oestrus suggests a role for dopamine in the generation of the oestrous prolactin surge.
Assuntos
Dopamina/metabolismo , Estro/fisiologia , Hipotálamo/citologia , Neurônios/metabolismo , Prolactina/metabolismo , Animais , Diestro/fisiologia , Feminino , Eminência Mediana/metabolismo , Neurônios/citologia , Prolactina/sangue , Proteínas Proto-Oncogênicas c-fos/metabolismo , Ratos , Ratos Wistar , Tirosina 3-Mono-Oxigenase/metabolismoRESUMO
A secretory surge of prolactin occurs on the afternoon of oestrous in cycling rats. Although prolactin is regulated by ovarian steroids, plasma oestradiol and progesterone levels do not vary during oestrous. Because prolactin release is tonically inhibited by hypothalamic dopamine and modulated by dopamine transmission in the preoptic area (POA), the present study aimed to evaluate whether oestrogen receptor (ER)-alpha and progestin receptor (PR) expression in the dopaminergic neurones of arcuate (ARC), periventricular, anteroventral periventricular (AVPe) and ventromedial preoptic (VMPO) nuclei changes during the day of oestrous. Cycling rats were perfused every 2 h from 10-20 h on oestrous. Brain sections were double-labelled to ERalpha or PR and tyrosine hydroxylase (TH). The number of TH-immunoreactive (ir) neurones did not vary significantly in any area evaluated. ERalpha expression in TH-ir neurones increased at 14 and 16 h in the rostral-ARC and dorsomedial-ARC, 14 h in the caudal-ARC and 16 h in the VMPO, whereas it was unaltered in the ventrolateral-ARC, periventricular and AVPe. PR expression in TH-ir neurones of the periventricular and rostral, dorsomedial, ventrolateral and caudal-ARC decreased transitorily during the afternoon, showing the lowest levels between 14 and 16 h; but it did not vary in the AVPe and VMPO. Plasma oestradiol and progesterone concentrations were low and unaltered during oestrous, indicating that the changes in receptors expression were probably not due to variation in ligand levels. Thus, our data suggest that variations in ERalpha and PR expression may promote changes in the activity of medial basal hypothalamus and POA dopaminergic neurones, even under unaltered secretion of ovarian steroids, which could facilitate the occurrence and modulate the magnitude of the prolactin surge on oestrous.
Assuntos
Dopamina/metabolismo , Receptor alfa de Estrogênio/metabolismo , Ciclo Estral/metabolismo , Hipotálamo/metabolismo , Neurônios/metabolismo , Área Pré-Óptica/metabolismo , Receptores de Progesterona/metabolismo , Animais , Feminino , Modelos Biológicos , Ratos , Ratos Wistar , Fatores de TempoRESUMO
Skinned fiber preparations are used to obtain the maximal contractile activation of isolated myocardial preparations. Tetanic contractions elicited in the presence of sarcoplasmic reticulum inhibitors have also been used as an alternative method to produce maximal active tension in the intact myocardium. In this work our purpose was to define the best conditions to obtain tetanic contractions in the rat myocardium and to compare the influence of muscle length and inotropic interventions (Ca2+ and Bay K 8644) in the tension produced in twitches and tetanic contractures. Papillary muscles were mounted in a perfusion chamber to record isometric force. Tetanic contractions were elicited by using suprathreshold stimulation with rectangular pulses (10 ms duration) at 5 Hz in the presence of 2.5 mM caffeine. Caffeine depressed the twitch tension but the tetanic tension was similar to that produced under steady-state stimulation (0.5 Hz) in control conditions. Tetanic and twitch tensions were similar along the whole extension of the length-tension curve and under the positive inotropic effects produced by Ca2+ (0.25 to 3.75 mM) or by the Ca(2+)-channel agonist Bay K 8644 (1 microM). During long tetanic stimuli (60 s) a time-dependent tension decay was observed. This decay was prolonged by reducing the extracellular K+ from 5.4 to 1.0 microM, suggesting that Ca2+ extrusion through the Na-Ca exchanger seems to occur during tetanic stimulation. Since tetanic tension was never higher than the tension obtained in twitches elicited at the same Ca2+ concentration (0.5 Hz), we conclude that tetanic contractures represent a useful tool to investigate the contractile response of intact myocardial preparations with a nonfunctional sarcoplasmic reticulum.(ABSTRACT TRUNCATED AT 250 WORDS)
Assuntos
Cafeína/farmacologia , Coração/efeitos dos fármacos , Retículo Sarcoplasmático/efeitos dos fármacos , Animais , Cálcio/farmacologia , Relação Dose-Resposta a Droga , Feminino , Troca Iônica , Masculino , Contração Muscular , Cloreto de Potássio/farmacologia , Ratos , Ratos Wistar , Fatores de TempoRESUMO
The changes occurring in the collagen content in the residual myocardium after infarction have been poorly studied. The aim of this study was to determine the changes in the collagen content in the right and left ventricular muscle of chronically infarcted hearts. Male albino rats were submitted to ligature of the left coronary artery to produce infarction (Inf). Controls underwent a sham surgery (Sh). Inf rats were divided into groups designed to receive chronic therapy with propranolol (Prop, 1 g/l, n = 10) or hydralazine (Hydr, 0.125 g/l, n = 10) dissolved in the drinking water. One group of Inf rats (n = 12) and the Sh group (n = 10) received no treatment. The animals were killed 1 month after surgery to obtain the cardiac wet weights and to determine protein and hydroxyproline (OH-Pro) concentrations in the right ventricle (RV) free wall and in the left ventricular remaining muscle (LV), including the interventricular septum. Inf determined a 42% increase of the RV weight to body weight ratio (Sh = 0.57 +/- 0.04 mg/g; Inf = 0.81 +/- 0.06 mg/g; p < 0.05) and a 64% increase of OH-Pro concentration (Sh = 450 +/- 25 micrograms/g; Inf = 738 +/- 32 micrograms/g; p < 0.05). In Inf hearts the LV OH-Pro concentration increased similarly as in the RV. No effect of drug therapy was observed in the LV. In the RV however, propranolol reduced the hypertrophy and the OH-Pro concentration by the same amount (around 30%). Hydr on the other hand reduced OH-Pro and tended to increase hypertrophy. We conclude that a similar collagen deposition occurs in the myocardium of both ventricles after infarction in rats. Prop and Hydr were able to partially reduce this collagen increase in the right but not in the left ventricle.
Assuntos
Colágeno/metabolismo , Hidralazina/uso terapêutico , Infarto do Miocárdio/tratamento farmacológico , Miocárdio/metabolismo , Propranolol/uso terapêutico , Animais , Masculino , Infarto do Miocárdio/metabolismo , Ratos , Ratos WistarRESUMO
1. The role of the sarcoplasmic reticulum (SR) in the inotropic responses produced by changes in stimulation rate and rhythm and resting tension was investigated in the rat myocardium. 2. Rat papillary muscles contracting isometrically (basic stimulation rate = 30/min) were superfused in vitro with normal Krebs solution and after addition of ryanodine (1 microM). Post-rest potentiation was obtained after pauses of 5, 10, 15, 30, 60 and 120 s, and the stimulation rate was changed from 6 to 90 bpm. Post-extrasystolic potentiation was induced by interpolating an extra stimulus after an interval of 413 +/- 15 ms. NiCl2 (2 mM) was used to confirm that contractions obtained after SR blockade with ryanodine were activated only by sarcolemmal calcium influx. 3. In the presence of ryanodine, the post-rest potentiation phenomenon disappears and the force-frequency relationship changes from the typical force decrease produced by rate increase to force increase. Under the effect of ryanodine, resting tension increased with the increase in stimulation rate. This behavior was enhanced by reducing extracellular KCl from 5.4 mM to 1 mM. This maneuver decreases Na(+)-K(+)-ATPase and increases intracellular Na+ activity, which reduces Ca2+ extrusion through the Na(+)-Ca2+ exchange mechanism. 4. SR participation in the post-extrasystolic potentiation phenomenon is also suggested because ryanodine treatment reversed the extrasystolic force depression into potentiation. In the presence of ryanodine, blockade of Ca2+ influx with NiCl2 (2 mM) abolished isometric contractions indicating that after SR blockade contractions are mainly dependent on sarcolemmal Ca2+ influx. 5. The results suggest that the SR is involved in the genesis of post-rest potentiation and contributes to the typical force-frequency relationship of the rat myocardium and to the post-extrasystolic potentiation phenomenon. Moreover, SR activity seems to be important for the maintenance of low resting tension in the cardiac muscle, which may represent a safety factor against contractures during inotropic changes produced in rate and rhythm.
Assuntos
Coração/fisiologia , Contração Miocárdica/fisiologia , Retículo Sarcoplasmático/fisiologia , Animais , Bloqueadores dos Canais de Cálcio/metabolismo , Feminino , Frequência Cardíaca/fisiologia , Masculino , Músculos Papilares/fisiologia , Ratos , Ratos Wistar , Rianodina/farmacologiaRESUMO
1. The role of the sarcoplasmic reticulum (SR) in the inotropic responses produced by changes in stimulation rate and rhythm and resting tension was investigated in the rat myocardium. 2. Rat papillary muscles contracting isometrically (basic stimulation rate = 30/min) were superfused in vitro with normal Krebs solution and after addition of ryanodine (1 microM). Post-rest potentiation was obtained after pauses of 5, 10, 15, 30, 60 and 120 s, and the stimulation rate was changed from 6 to 90 bpm. Post-extrasystolic potentiation was induced by interpolating an extra stimulus after an interval of 413 +/- 15 ms. NiCl2 (2 mM) was used to confirm that contractions obtained after SR blockade with ryanodine were activated only by sarcolemmal calcium influx. 3. In the presence of ryanodine, the post-rest potentiation phenomenon disappears and the force-frequency relationship changes from the typical force decrease produced by rate increase to force increase. Under the effect of ryanodine, resting tension increased with the increase in stimulation rate. This behavior was enhanced by reducing extracellular KCl from 5.4 mM to 1 mM. This maneuver decreases Na(+)-K(+)-ATPase and increases intracellular Na+ activity, which reduces Ca2+ extrusion through the Na(+)-Ca2+ exchange mechanism. 4. SR participation in the post-extrasystolic potentiation phenomenon is also suggested because ryanodine treatment reversed the extrasystolic force depression into potentiation. In the presence of ryanodine, blockade of Ca2+ influx with NiCl2 (2 mM) abolished isometric contractions indicating that after SR blockade contractions are mainly dependent on sarcolemmal Ca2+ influx. 5. The results suggest that the SR is involved in the genesis of post-rest potentiation and contributes to the typical force-frequency relationship of the rat myocardium and to the post-extrasystolic potentiation phenomenon. Moreover, SR activity seems to be important for the maintenance of low resting tension in the cardiac muscle, which may represent a safety factor against contractures during inotropic changes produced in rate and rhythm.
Assuntos
Animais , Feminino , Masculino , Ratos , Contração Miocárdica/fisiologia , Coração/fisiologia , Retículo Sarcoplasmático/fisiologia , Bloqueadores dos Canais de Cálcio/metabolismo , Frequência Cardíaca/fisiologia , Músculos Papilares/fisiologia , Ratos Wistar , RianodinaRESUMO
The aim of the study was to examine, in papillary muscles and in a whole heart preparation, the effects of isoproterenol on the myocardial mechanical activity at different extracellular Ca2+ concentrations. Papillary muscles from left ventricles, contracting isometrically, and rat hearts perfused by the Langendorff technique developing isovolumetric pressure at a fixed rate (200 bpm) and diastolic pressure of 5 mmHg were studied at different Ca2+ concentrations for analysis of the effects of increasing doses of isoproterenol. Papillary muscles were treated with isoproterenol (0.5 to 8 ng ml-1) at four extracellular Ca2+ concentrations (0.25, 0.5, 1.25 and 2.5 mM) and Langendorff perfused hearts were stimulated by isoproterenol (0.05 ng ml-1 to 0.8 ng ml-1), also at four extracellular Ca2+ concentrations (0.5, 1.25, 2.5 and 3.75 mM). Both papillary muscles and perfused hearts showed that force and isovolumetric systolic pressure increase in response to isoproterenol at low Ca2+ concentrations. As Ca2+ concentration is increased, isoproterenol's positive inotropic effect subsides. However, papillary muscle isometric contractions showed a similar time to peak tension decrease in response to isoproterenol at all external Ca2+ concentrations used. The results suggest that the positive inotropic response to isoproterenol, in isolated preparations, changes as a function of extracellular Ca2+ concentration decreasing as external Ca2+ increases. Time to peak tension reduction reinforces the idea that this small positive inotropic response to isoproterenol of the rat myocardium, at the physiological Ca2+ concentration, is due to the Ca2+ saturation of the mechanical activity.
Assuntos
Cálcio/administração & dosagem , Coração/fisiologia , Isoproterenol/administração & dosagem , Músculos Papilares/fisiologia , Animais , Cálcio/farmacologia , Relação Dose-Resposta a Droga , Feminino , Coração/efeitos dos fármacos , Técnicas In Vitro , Contração Isométrica/efeitos dos fármacos , Isoproterenol/farmacologia , Masculino , Músculos Papilares/efeitos dos fármacos , Perfusão , Ratos , Ratos WistarRESUMO
1. Post-rest potentiation reflects basic cellular mechanisms that control cardiac muscle contraction. Transmembrane calcium influx, the Na+/Ca2+ exchange and the function of intracellular stores that liberate activator calcium upon activation are some of the mechanisms involved. 2. Three aspects of the post-rest potentiated phenomenon were investigated, using isometrically contracting rat papillary muscles and toad ventricle strips: dependence on 1) inotropic state of steady-state contractions, 2) pause duration and Na+/Ca2+ exchange activity, and 3) the extent of transmembrane calcium influx. 3. The results suggest that the potentiated state of post-rest contractions increases linearly with the inotropic state of preceding steady-state control contractions. As the pause duration increases from 5 to 240 s, the post-rest potentiation also increases, attaining a steady level after 30-s pauses. During the pause, the Na+/Ca2+ exchange mechanism operates at an activity level that can alter the amount of activator calcium used for post-rest contractions. Interventions that increase intracellular Na+, such as the increase of the stimulation rate from 0.5 to 1 Hz or the increase of extracellular NaCl concentration to 160 mM, reduce the Na+/Ca2+ activity, increasing intracellular Ca2+ and post-rest potentiation. The decrease of transmembrane Ca2+ influx during activation increases the relative participation of the sarcoplasmic reticulum in the development of post-rest potentiation. Reduction of extracellular Ca2+ concentration from 1.25 mM to 0.25 mM or the use of 1 microM verapamil and 2 mM manganese increases the relative potentiation of post-rest contractions. This is particularly observed in toad ventricle strips since post-rest potentiation, which does not develop under control conditions, is observed after verapamil or manganese treatment. The results suggest that the excitation-contraction coupling process operating for post-rest contraction activation, unlike that operating for steady-state contraction activation, depends more on the calcium stored at intracellular sites than on transmembrane calcium influx.
Assuntos
Contração Miocárdica/fisiologia , Músculos Papilares/fisiologia , Animais , Bufo marinus , Cálcio/metabolismo , Bloqueadores dos Canais de Cálcio/farmacologia , Feminino , Transporte de Íons/efeitos dos fármacos , Masculino , Potenciais da Membrana , Ratos , Descanso , Sódio/metabolismoRESUMO
Post-rest potentiation reflects basic cellular mechanisms that control cardiac muscle contraction. Transmembrane calcium influx, the Na+/Ca*+ exchange and the function of intracellular stores that liberate activator calcium upon activation are some of the mechanisms involved. Three aspects of the post-rest potentiated phenomenon were investigated, using isometrically contracting rat papillary muscles and toad ventricle strips: dependence on 1) inotropic state of steady-state contractions, 2) pause duration and Na+/Ca*+ exchange activity, and 3) the extent of transmembrane calcium influx. The results suggest that the potentiated state of post-rest contractions increases linearly with the inotropic state of preceding steady-state control contractions. As the pause duration increases from 5 to 240 s, the post-rest potentiation also increases, attaining a steady level after 30-s pauses. During the pause, the Na+/Ca*+ exchange mechanism operates at an activity level that can alter the amount of activator calcium used for post-rest contractions. Interventions that increase intracellular Na+, such as the increase of the stimulation rate from 0.5 to 1 Hz or the increase of extracxellular NaCl concentration to 160 mM, reduce the Na+/Ca*+ activity, increasing intracellular Ca*+ and post-rest potentiation. The decrease of transmembrane Ca*+ and post-rest potentiation. The decrease of transmembrane Ca*+ influx during activation increases the relative participation of the sarcoplasmic reticulum in the development of post-r5est potentiation. Reduction of extracellular Ca*+ concentration from 1.25 mM to 0.25 mM or the use of 1 uM verapamil and 2 mM manganese increases the relative potentiation of post-rest contractions. This is particulary observed in toad ventricle strips since post-rest potentiation, which does not develop under control conditions, is observed after verapamil or manganese treatment. The results suggest that the excitation contraction coupling process operating for post-rest contraction activation, unlike that operating for steady-state contraction activation, depends more on the calcium stored at intracellular sites than on transmembrane calcium influx
Assuntos
Ratos , Contração Miocárdica/etiologia , Manganês/administração & dosagem , Músculos Papilares , Descanso , Verapamil/administração & dosagem , Cálcio , Contração MiocárdicaRESUMO
PURPOSE: To investigate the effects of chronic subcutaneous administration of reserpine (Res) or propranolol (Prop) on the postinfarction myocardial hypertrophy and the effects of Prop treatment on myocardial contractility in rats. METHODS: Male albino rats (3-month-old) were submitted to left coronary artery ligation to produce myocardial infarction. Rats submitted to a sham-operation were used as controls. Animals submitted to Res (0.5 mg/kg/day) were killed 8-10 days after surgery and those submitted to Prop (2.5 mg/kg twice a day) were killed 15 (G-15) or 30 (G-30) days later. Hypertrophy was evaluated according to cardiac chambers weight corrected to body weights. Isometric force (F) developed by isolated right ventricular (RV) strips was used as a contractile index. RESULTS: Atrial and RV hypertrophy were completely blocked by Res. Prop treatment did not significantly change infarct extension, evaluated by the fibrous scar area. Prop therapy also reduced atrial and RV hypertrophy. This effect was less intense compared to Res, however. In the G-30, for example, the relative right atrial and RV weights (mg/g) were 0.10 +/- 0.01 and 0.59 +/- 0.03 in sham-operated animals (n = 9), 0.12 +/- 0.01 and 0.079 +/- 0.07 in infarcted animals with Prop (n = 11) and 0.22 +/- 0.03 and 1.11 +/- 0.07 in those infarcted and treated with saline solution (n = 11). Basal F values were 25 to 30% lower in RV strips from infarcted than in sham-operated hearts. This reduction however was only 4% (G-15) and 8% (G-30) in infarcted hearts under Prop treatment. CONCLUSION: These data show that sympathetic blockade reduces the postinfarction myocardial hypertrophy and tends to preserve contractility of the surviving myocardium.