Evaluation of the long-lasting antihypertensive action of 7-O-ethylfangchinoline

Antihypertensive activity of a nonpeptide angiotensin II receptor antagonist, YM358, in rats and dogs

The antihypertensive activity of YM358, 2,7-diethyl-5-[[2'-(1 H-tetrazol-5-yl)biphenyl-4-yl]methyl]-5H-pyrazolo[1,5-b][1,2,4]tri azole potassium salt monohydrate, a new nonpeptide angiotensin II receptor antagonist, was characterized in rats and dogs. In conscious rats, YM358 after a single oral administration (1-30 mg/kg) lowered blood pressure. The rank order of hypotensive potency of YM358 in conscious rats was 2-kidney, 1-clip renal hypertensive rats > spontaneously hypertensive rats > normotensive rats on the basis of maximum hypotension. YM358 also caused decreases in blood pressure in 2-kidney, 1-clip renal hypertensive dogs and furosemide-treated dogs. Repeated administration of YM358 to 2-kidney, 1-clip renal hypertensive rats for 28 days produced a stable and long-lasting antihypertensive effect without influencing circadian blood pressure and heart rate rhythms. No reflex tachycardia was observed in any animals of either species treated with YM358. Therefore, the pharmacological profile of this compound indicates that YM358 has potential as a useful antihypertensive agent.

Pharmacological studies on a new antihypertensive agent, S-2150, a benzothiazepine derivative: 2. Hypotensive effects in normotensive and hypertensive rats

S-2150 is a new 1,5-benzothiazepine derivative possessing both calcium channel-blocking and alpha 1-adrenoceptor-blocking effects. In isolated rat thoracic aorta precontracted with KCl (18 mM), the 50% inhibitory concentration (IC50) value was 190 nM for S-2150, which was similar to that of diltiazem. In aorta precontracted with phenylephrine (0.3 microM), IC50 values of S-2150 and diltiazem were 29 nM and > 10 microM, respectively. The relative contribution of calcium channel-blocking and alpha 1-adrenoceptor-blocking activities to hypotension was determined by using anesthetized rats before and after masking of the alpha 1-receptors with prazosin. The hypotensive effect of S-2150 [0.3 and 1 mg/kg intravenously (i.v.)] was attenuated by 40% after prazosin treatment, whereas that of diltiazem was not. In conscious spontaneously hypertensive rats (SHRs), renal hypertensive rats, and normotensive rats, S-2150 [10, 30, and 60 mg/kg orally (p.o.)] caused dose-dependent hypotensive effects. The effect of S-2150 was 4-7 times more potent than that of diltiazem. There were no changes in the hypotensive effects with consecutive administration of S-2150 during 6-8 weeks in SHRs and stroke-prone SHRs (SHRSPs). In SHRSPs, S-2150 reduced the mortality by stroke and small arterial hyperplasia in abdominal organs and also ameliorated renal excretory function. These results suggest that S-2150 may be a useful antihypertensive agent possessing both calcium-antagonistic and alpha 1-adrenoceptor-blocking effects.

Effect of repeated administration of KT3-671, a nonpeptide AT1 receptor antagonist, on diurnal variation in blood pressure, heart rate, and locomotor activity in stroke-prone spontaneously hypertensive rats as determined by radiotelemetry

KT3-671, a nonpeptide AT1 receptor antagonist, was administered to 20-week-old stroke-prone spontaneously hypertensive rats (SHRSP) daily for 3 weeks. Its effects on systolic, mean, and diastolic arterial blood pressure (SAP, MAP, DAP), heart rate and locomotor activity were investigated with radiotelemetry. A clear diurnal variation in blood pressure, heart rate, and locomotor activity was observed in synchrony with the light cycle. KT3-671 at a daily dose of 10 mg/kg orally (p.o), produced a significant and consistent reduction in blood pressure, preventing the development of hypertension. KT3-671 reduced SAP more than DAP, suggesting that it may affect both vascular tone and cardiac output. Although KT3-671 did not affect diurnal rhythms in heart rate and locomotor activity, it did cause a slight but significant reduction in heart rate. The MAP determined 23 h after the administration of KT3-671 showed a significant reduction from the day 2 of therapy to the day 3 after discontinuation of therapy, suggesting a long duration of antihypertensive action. There was no rebound increase in blood pressure after discontinuation of KT3-671 therapy. These results suggest that KT3-671 may be potentially useful in the therapy of hypertension.