RESUMEN
The responses of isolated pressurized second order mesenteric resistance arteries of Wistar rats, superfused with physiological salt solution (PSS) were determined to 5-hydroxytryptamine (5-HT) and norepinephrine (NE). The contractility of the vessel was enhanced in response to 5-HT compared to NE (P<.001, ANOVA). The L-type calcium ion channel blocker, nifedipine (10(-6) M) abolished the response to either 5-HT or NE. In vessels with intact endothelium, thapsigargin (TG, 10(-6) M), which inhibits uptake of calcium ions into intracellular stores, significantly reduced the contractile response to 5-HT (P<.02) but had little or no effect on the response to NE (P=.2). However, in vessels denuded of the endothelium, there was no significant difference in the response of the mesenteric artery, after TG, to either 5-HT or NE. The results indicate that, in the rat mesenteric resistance vessel, both 5-HT and NE use calcium ions from extracellular sources for contraction, while NE relies mainly on extracellular ion influx with little or no contribution from intracellular sources. The reduced response of the de-endothelized vessel to 5-HT after TG suggests that the utilization of intracellular stores by this agonist is endothelium-dependent. These observations may explain the enhanced responsiveness of the mesenteric artery to 5-HT when compared with NE.
Asunto(s)
Arterias Mesentéricas/efectos de los fármacos , Nifedipino/farmacología , Norepinefrina/farmacología , Serotonina/farmacología , Tapsigargina/farmacología , Animales , Relación Dosis-Respuesta a Droga , Masculino , Arterias Mesentéricas/fisiología , Ratas , Ratas Wistar , Vasoconstricción/efectos de los fármacos , Vasoconstricción/fisiologíaRESUMEN
1. The effect of chronic ethanol (10%) consumption for 5 months on vascular smooth muscle (VSM) using aortic rings of both sexes of Sprague-Dawley rats was studied. 2. Chronic ethanol consumption increased the sensitivity of VSM to noradrenaline (NA) in both male and female ethanol-treated rats. 3. There was no significant difference in the contractile response of male and female ethanol-treated rats to NA. Hence, the enhancement of vascular contractility to the agonist due to chronic ethanol consumption is independent of gender. 4. Vascular relaxation induced by acetylcholine showed similar responses in all experimental groups. Thus, chronic ethanol consumption seems to have no significant effect on the production of endothelium-dependent relaxing factor. 5. However, the VSM sensitivity to potassium chloride was increased in female ethanol-treated rats, whereas male ethanol-treated rats had similar responses as controls. 6. The results suggest that the effect of chronic ethanol consumption on VSM varies with gender. Impairment of VSM in male ethanol-treated rats is due partly to changes in the receptor-operated channel, whereas in females it is due to changes in both receptor- and potential-operated channels.
Asunto(s)
Etanol/administración & dosificación , Músculo Liso Vascular/efectos de los fármacos , Vasoconstricción/efectos de los fármacos , Vasodilatación/efectos de los fármacos , Animales , Aorta/efectos de los fármacos , Aorta/fisiología , Relación Dosis-Respuesta a Droga , Femenino , Técnicas In Vitro , Masculino , Músculo Liso Vascular/fisiología , Ratas , Ratas Sprague-Dawley , Factores Sexuales , Vasoconstricción/fisiología , Vasodilatación/fisiologíaRESUMEN
Blood pressure and heart rate changes during pregnancy were investigated in fructose-fed (diabetic) Sprague-Dawley rats. A total of 48 pubertal female rats were used. The experimental rats were fed with 25% (w/w) fructose mixed with normal rat chow for minimum period of 3 weeks while the control rats were fed with the normal rat chow. They all had free access to drinking water. Systolic, diastolic and mean arterial blood pressures and the heart rates were measured in both non-pregnant and pregnant control rats and their diabetic counterparts. The results indicate that systolic blood pressures significantly increased progressively during pregnancy in fructose-fed rats as compared with the non-pregnant rats (P < 0.0001) while in the control rats, except for the 2nd trimester sub-group, which had a similar value with the non-pregnant sub-group, the systolic blood pressure (SBP) also, increased steadily. When the diabetic group is compared with the control group, the SBP (in the 2nd trimester sub-groups) was raised from 82.18 +/- 1.26 mmHg in control rats to 112.48 +/- 1.26 mmHg in the diabetic rats (P < 0.0001). Diastolic blood pressure (DBP) progressively increased significantly in the diabetic rats from 63.94 +/- 3.95 mmHg in the non-pregnant sub-group to 91.95 +/- 1.89 mmHg in the 3rd trimester sub-group of the pregnant rats (P < 0.0001). The DBP of the 2nd trimester sub-group of the diabetic rats was significantly raised from 61.88 +/- 4.20 mmHg in the control rats to 89.60 +/- 1.79 mmHg in the diabetic rats (P < 0.0001). In addition, the mean arterial blood pressure (MAP) was significantly raised in the 1st and 2nd trimester of the diabetic rats from 70.61 +/- 3.12 mmHg in the non-pregnant diabetic rats to 96.28 +/- 1.36 mmHg and 97.13 +/- 1.15 mmHg respectively, (P < 0.0001, P < 0.0001). There was a progressive increase in the heart rates, in both control and diabetic groups, from non-pregnant sub-groups to the 3 trimesters of pregnancy. The body weights of the 2 groups of rats increased significantly as pregnancy progressed. These results suggest that fructose-induced diabetes could cause the development of sustained hypertension during pregnancy via the insulin-resistance-hyperinsulinemia-link.
Asunto(s)
Presión Sanguínea/fisiología , Diabetes Mellitus Experimental/fisiopatología , Fructosa , Frecuencia Cardíaca/fisiología , Embarazo en Diabéticas/fisiopatología , Animales , Peso Corporal , Femenino , Fructosa/administración & dosificación , Hipertensión/etiología , Hipertensión/fisiopatología , Resistencia a la Insulina/fisiología , Embarazo , Ratas , Ratas Sprague-DawleyRESUMEN
1. The present study examined the effects of concurrent manipulation of dietary calcium and salt on contractile responses of vascular smooth muscle (VSM) and endothelial function of aortic rings from Sprague-Dawley rats. 2. Salt loading enhanced the contractile response of the aortic rings to noradrenaline (NA), an effect that was blunted by a high calcium intake. 3. Removal of the endothelium and incubation of aortic rings in physiological salt solution containing methylene blue increased the sensitivity of the rings to NA. 4. The increase in the sensitivity of aortic rings induced by endothelium removal was more pronounced in aortic rings from salt-loaded rats. 5. Acetylcholine caused similar degrees of relaxation in all experimental groups, but the relaxation to histamine was smaller (P < 0.05) in salt-loaded rats than in other groups of rats; however, after removal of the endothelium, the contractile response to histamine was higher in salt-loaded rats. 6. The results indicate that the hypersensitivity of isolated aortic rings to agonists, as observed in salt-loaded rats, is due to altered responses of the VSM and not as a result of changes in the endothelium. In addition, salt loading tends to increase the synthesis of endothelium-dependent relaxing factor. The ability of salt loading to enhance the contractile responses of VSM to agonists can be prevented by supplementing the diet with high calcium.
Asunto(s)
Calcio/administración & dosificación , Dieta , Endotelio Vascular/fisiología , Músculo Liso Vascular/fisiología , Cloruro de Sodio/administración & dosificación , Acetilcolina/farmacología , Animales , Relación Dosis-Respuesta a Droga , Histamina/farmacología , Masculino , Azul de Metileno/farmacología , Contracción Muscular/efectos de los fármacos , Relajación Muscular/efectos de los fármacos , Ratas , Ratas Sprague-DawleyRESUMEN
The effect of calcium supplementation and salt loading on blood pressure, serum electrolytes, and vasoconstrictor response to serum and vascular prostaglandin synthesis were studied in Sprague Dawley rats. The mean arterial pressure of salt-loaded rats was higher (P < 0.05) than the mean arterial pressure of normal rats, salt-loaded-calcium-fed rats, or calcium-fed rats. Serum from salt-loaded rats had lower serum potassium (4.47 +/- 0.39 Meq/L) and salt-loaded-calcium-fed rats (5.14 +/- 0.47 Meq/L). The vasoactivity of serum from the salt-loaded rats (1116.67 +/- 160.13 mg) was higher than the contraction produced by sera from normal rats (643.80 +/- 37.50 mg) or from salt-loaded-calcium fed rats (562.47 +/- 37.50 mg). Indomethacin did not alter the contractile response of aortae from normal rats and salt-loaded rats to noradrenaline, but it significantly enhanced the contractile response of aortae from salt-loaded-calcium-fed and calcium-fed rats. The results suggest that dietary calcium may lower blood pressure by reducing the circulating levels of some plasma vasoactive factors induced by salt loading and by enhancing the synthesis of vasodilator prostaglandins.
Asunto(s)
Calcio de la Dieta/farmacología , Sodio en la Dieta/antagonistas & inhibidores , Vasoconstrictores/antagonistas & inhibidores , Vasodilatadores/farmacología , Análisis de Varianza , Animales , Aorta Torácica/efectos de los fármacos , Presión Sanguínea/efectos de los fármacos , Calcio/sangre , Fármacos Cardiovasculares/farmacología , Frecuencia Cardíaca/efectos de los fármacos , Indometacina/farmacología , Norepinefrina/farmacología , Potasio/sangre , Prostaglandinas/biosíntesis , Distribución Aleatoria , Ratas , Ratas Sprague-Dawley , Sodio/sangre , Sodio en la Dieta/administración & dosificación , Vasoconstrictores/farmacologíaRESUMEN
This study was performed to investigate the effect of chloroquine (CQ) on the contractility of isolated smooth muscles of the rat uterus, urinary bladder; and trachea. Chloroquine, 4 x 10(-4) mol.l-1 completely abolished uterine contractions produced by 10(-2) IU/ml oxytocin, and 10(-6) mol.l-1 5-hydroxytryptamine (5-HT) and acetylcholine (Ach). Chloroquine also caused a concentration-dependent relaxation of 10(-6) mol.l-1 Ach-contracted rat trachea. Cumulative addition of CQ (10(-8)-10(-3) mol.l-1) to spontaneously contracting rat urinary bladder did not produce any significant effect. It also did not affect the contractile response of the bladder to Ach and 5-HT. The results suggest that CQ inhibits the contractile process in the rat uterus and trachea but not the urinary bladder.
Asunto(s)
Cloroquina/farmacología , Músculo Liso/efectos de los fármacos , Tráquea/efectos de los fármacos , Vejiga Urinaria/efectos de los fármacos , Contracción Uterina/efectos de los fármacos , Animales , Femenino , Técnicas In Vitro , Contracción Muscular/efectos de los fármacos , Músculo Liso/fisiología , Ratas , Ratas Sprague-Dawley , Tráquea/fisiología , Vejiga Urinaria/fisiologíaRESUMEN
The antihypertensive effect of aqueous extracts of the calyx of Hibiscus sabdariffa (HS) has been investigated in anaesthetized rats. Hibiscus sabdariffa caused a dose-dependent decrease in mean arterial pressure (MAP) of the rats. Sectioning of the right and left vagi nerves did not have a significant effect on the fall in MAP produced by HS. Cholinergic blockade with 0.2 mgkg-1 atropine and histaminergic blockade with 1 mgkg-1 cimetidine and 15 mgkg-1 promethazine significantly attenuated the hypotensive response to HS. Pretreatment of the rats with 20 mgkg-1 HS extract did not have a significant effect on increase in blood pressure induced by bilateral carotid occlusion (48.05 +/- 6.83 mmHg vs 46.53 +/- 7.49 mmHg). The cumulative addition of HS to noradrenaline precontracted aortic rings produced dose-dependent relaxation of the rings. The maximum relaxation response was 86.96 +/- 5.20% and this was observed at the dose of 1.70 mgml-1. These findings suggest that the antihypertensive effect of the extracts of calyx of HS is not mediated through inhibition of the sympathetic nervous system but it could be mediated through acetylcholine-like and histamine-like mechanisms as well as via direct vaso-relaxant effects.
Asunto(s)
Presión Sanguínea/efectos de los fármacos , Medicinas Tradicionales Africanas , Extractos Vegetales/farmacología , Animales , Atropina/farmacología , Cimetidina/farmacología , Relación Dosis-Respuesta a Droga , Evaluación Preclínica de Medicamentos , Antagonistas de los Receptores Histamínicos H1/farmacología , Antagonistas de los Receptores H2 de la Histamina/farmacología , Antagonistas Muscarínicos/farmacología , Nigeria , Prometazina/farmacología , Ratas , Ratas Sprague-DawleyRESUMEN
The effects of dietary salt-loading and concurrent administration of dietary calcium on water and electrolyte excretion in Sprague-Dawley rats have been studied. The total salt consumed by salt-loaded rats was significantly higher than that of control rats (P < 0.05). The total salt consumed by salt-loaded calcium fed rats was also higher (P < 0.05) than that of control rats but it was slightly lower (P < 0.05) than the consumption by the salt-loaded. Rats fed only high calcium diet had the least salt consumption. The total water intake was also highest (P < 0.05) in the salt-loaded rats when compared with either control rats, salt-loaded-calcium-fed rats or calcium-fed rats. Urinary water excretion was highest (P < 0.05) in salt-loaded-calcium-fed rats followed by salt-loaded rats and calcium-fed rats while the control rats had the least. Similarly, the sodium excretion was highest in salt-loaded-calcium-fed rats followed by salt-loaded rats and calcium-fed rats and control rats respectively. Potassium excretion was highest in salt-loaded-calcium-fed rats followed by salt-loaded rats and calcium-fed rats while the control rats had the least excretion of potassium. Serum sodium concentrations were identical in all the groups although in salt-loaded rats and salt-loaded-calcium-fed rats the values were slightly higher than those of controls. However, serum potassium concentration was lowest in salt-loaded rats and calcium-fed rats while the values for salt-loaded-calcium-fed rats was not significantly different from that of control. The results of this study suggest that increase in dietary calcium intake reduces the increase in blood pressure resulting from salt-loading and this is accompanied by an increase in water and sodium excretion.
Asunto(s)
Calcio de la Dieta/uso terapéutico , Hipertensión/dietoterapia , Hipertensión/etiología , Cloruro de Sodio Dietético/efectos adversos , Equilibrio Hidroelectrolítico/efectos de los fármacos , Animales , Presión Sanguínea/efectos de los fármacos , Calcio de la Dieta/farmacología , Modelos Animales de Enfermedad , Conducta de Ingestión de Líquido/efectos de los fármacos , Ingestión de Energía/efectos de los fármacos , Conducta Alimentaria/efectos de los fármacos , Femenino , Hipertensión/metabolismo , Masculino , Potasio/sangre , Potasio/orina , Ratas , Ratas Sprague-Dawley , Sodio/sangre , Sodio/orinaRESUMEN
Sprague-Dawley rats were made hypertensive by 6-week dietary salt loading with 8% NaCl in the diet and compared with control rats which had normal feed and water. At the end of this period, the salt-loaded group developed hypertension but the heart rate did not differ significantly from control. Serum taken from salt-loaded rats showed enhanced vasoconstrictor effect on normal rat's aorta when compared with controls. This enhanced vasoconstrictor effect was attenuated by adrenergic receptor blockers but not by serotoninergic blockers. Thus salt loading may induce accumulation of vasoactive agents in the blood of rats.
Asunto(s)
Hipertensión/sangre , Contracción Muscular , Músculo Liso Vascular/fisiología , Animales , Aorta/fisiología , Frecuencia Cardíaca , Hipertensión/inducido químicamente , Hipertensión/fisiopatología , Masculino , Ratas , Ratas Sprague-Dawley , Cloruro de Sodio , Vasoconstricción/fisiologíaRESUMEN
The effects of chloroquine on resting blood pressure, forearm blood flow (FBF), and forearm vascular resistance (FVR) and on the responses to cold stimulation were studied in healthy young adults. Chloroquine sulphate (800 mg) reduced systolic pressure and increased FBF (P < 0.05) but had no effect on resting FVR. Cold immersion increased systolic pressure (from 108.8 +/- 1.7 mmHg to 127.8 +/- 6.9 mmHg; P < 0.05) diastolic pressure (from 73.4 +/- 2.7 to 95.2 +/- 6.2 mmHg; P < 0.01) and FVR (from 5.9 +/- 0.9 to 13.0 +/- 1.9 a.u.; P < 0.001) but reduced FBF (from 14.3 +/- 1.64 to 10.1 +/- 1.29 ml min-1; P < 0.05). Chloroquine reduced the increase in FVR reduced by cold stimulation (P < 0.01), but had little effect on the BF and FBF responses to cold stimulation. The hypotensive effect of chloroquine could be attributed, at least in part, to the observed fall in vascular resistance.
Asunto(s)
Presión Sanguínea/efectos de los fármacos , Cloroquina/farmacología , Antebrazo/irrigación sanguínea , Resistencia Vascular/efectos de los fármacos , Adulto , Frío , Femenino , Humanos , Inmersión , Masculino , Estimulación Física , Flujo Sanguíneo Regional/efectos de los fármacosRESUMEN
We have studied the effects of mefloquine on isolated rat aorta. Mefloquine (10(-8) to 1.6 x 10(-4) mol.l-1) relaxed aortic rings precontracted with both noradrenaline (10(-7) mol.l-1) and potassium chloride (60 mmol.l-1). The mefloquine-induced relaxation was somewhat attenuated by removal of the endothelium. Contractile responses to noradrenaline, potassium chloride, and calcium chloride were reduced by incubating the aortic rings in physiological salt solution containing mefloquine, suggesting that mefloquine reduces calcium influx, which is required for excitation-contraction coupling. The results show that mefloquine relaxes vascular smooth muscle via mechanisms which are partly endothelium-dependent and which is also associated with inhibition of Ca2+ influx from the extracellular medium.
Asunto(s)
Mefloquina/farmacología , Músculo Liso Vascular/efectos de los fármacos , Animales , Aorta , Medios de Cultivo , Relación Dosis-Respuesta a Droga , Femenino , Masculino , Contracción Muscular , Relajación Muscular , Norepinefrina/farmacología , Cloruro de Potasio/farmacología , Ratas , Ratas Sprague-DawleyRESUMEN
Thirteen patients suffering from acute malaria attack and thirteen apparently healthy human volunteers (control) were used for the study. Platelet aggregation was determined by platelet count ratio technique in which a reduction in platelet count ratio signified an increase in platelet aggregation. Platelet count ratio in acute malaria patients was 0.75 +/- 0.03 (SEM). Platelet count ratio in subjects used as control was 0.88 +/- 0.02. This value was significantly higher than the former (P less than 0.001). Platelet count ratio correlated negatively with the degree of parasitaemia (r = -0.71; P less than 0.01). ADP, a platelet aggregating drug, also reduced platelet count ratio in rats significantly. Acute malaria attack therefore enhances platelet aggregation in vivo.