ABSTRACT
The effects of tetrandrine and neferine on the phenylephrine-induced contractions were studied in Sprague-Dawley rat aortic rings. It was found that both tetrandrine and neferine ( 2?10-5 mol/L ) markedly inhibited phase I ( release of intracellular calcium) and phase II (entry of extracellular calcium) contractions after a 20 min incubation. After a shorter incubation period, tetrandrine and nefrine inhibited only the phase II contractions. Compared with tetrandrine, neferine exhibited slower and weaker effects
ABSTRACT
A new positive inotropic agent, sulmazole (base or HC1, l mg/kg i.v) increased dp/dtmax and LVSP significantly in anesthetized open chest cats (Ac) and acute heart failure cats (Fc).HR was increased minimally. The dp/dtmax values were increased by 7% (base, Ac), 13% (HC1, Ac), and 45% (base, Fc) respectively. In addition, sulmazole decreased LVEDP, and increased CO and MAP in Fc, while it lowered MAP in a dose-dependent manner (Ac).The lowest doses of sulmazole induced arrhythmia were 10 mg/kg i.v (Ac), and 20 mg/kg i.v (Fc), and the arrhythmia was reversible. When the dose was increased to 30mg/ kg i.v (base), severe arrhythmia could be produced in most cats.The ratio between toxic dose and effective dose was 10-30.Ouabain, 30 ?g/kg i.v, increased dp/dtmax, LVSP and MAP, and decreased HR significantly i Ac. Ouabain, 60 ?g/kg i.v, produced severe irreversible arrhythmia and most cats died (n = 6/8). The ratio between toxic and effective dose was less than 2.
ABSTRACT
The effects of nitrendipine (Nit) and tetrandrine (Tet) on the contents of ?-aminobutyric acid (GABA) in the hypothalamus and cortex were studied in spontaneously hypertensive rats (SHR). The results showed that short-term (1 week) and long-term (20 weeks) treatments with Nit and Tet produced a decrease in blood pressure and an increase in GABA contents in the hypothalamus but not in the cortex. These findings suggest that the action of Nil and Tet on GABA contents in the hypothalamus may be partially contributed to their antihypertensive effects.
ABSTRACT
The effects of long-term treatments with 7 antihypertensive agents on the functions of endothelium-dependent relaxation were studied in spontaneously hypertensive rats (SHR). It was found that captopril, atenolol and dihydrochlorothiazide (DHT) could prevent the endothelium in SHR from impairing, but tetrandrine, nitrendipine, prazosin and dihydralazine could not. The improvement of the function of endothelium-dependent relaxation was not related to the blood pressure lowing.
ABSTRACT
The effects of tetrandrine (Tet) on blood pressure, plasma renin activity (PRA) and the contractility of the papillary mascle and portal vein were studied in rats. After 4 d administration of Tet 30 mg/kg, 2/d, ig, blood pressure was decreased markedly in anesthetized male SD rats, but there were no effects on heart rate and PRA. A single dose of Tet 15 mg/kg iv reduced blood pressure and heart rate significantly, while did not change PRA. This single dose produced similar hypotensive effect in rats with and without pretreatment of Tet 30 mg/kg, 2/d, 4d, indicating the absence of tolerance. Tet inhibited the paced papillary muscle contractility and the spontaneous portal vein contractility, and the EC50 were 5.33?10-6mol/L and 4.25?10-5 mol/L, respectively. So the vascular selectivity of Tet is 0.12.
ABSTRACT
The purpose of this study is to investigate the effects of intravenous tetrandrine (Tet) on the outcome of myocardial ischemia and reperfusion. Tet 4mg- kg-1 iv significantly reduced arrhythmias resulting from a coronary artery ligation and reperfusion. It is suggested that Tet may be a prospective anti-arrhythmic drug in ischemic heart disease.
ABSTRACT
The inhibitory effects of cicletanine (Cic) and bepridil (Bep) on norepinephrine (NE)-and KCl-induced contractions were studied in isolated thoracic aorta rings of male Sprague-Dowley rats. It was found that Cic had a more potent effect on NE-induced contraction than on KCHnduced contraction. In. contrast, Bep had a more potent action on KCHnduced contraction. When the aorta rings were incubated with Cic and Bep, a potentialized inhibitory effect was observed on KCh but not NE-induced contractions. These effects were independent of the presence of endothelium. The results suggest that Cic and Bep have different action sites and properties on vascular smooth muscles.