PORTAL HYPOTENSIVE EFFECTS OF TETRANDRINE AND VERAPAMIL IN PORTAL HYPERTENSIVE RATS

The portal hypotensive effects of tetrandrine and verapamil (both calc ium-channel blockers) were assessed in portal hypertensive rats. Porta l hypertension was induced by partial portal vein ligation in Sprague- Dawley rats. Both tetrandrine (4, 8, 16 and 24 mg kg(-1)) and verapami l (0.5, 1.0, 1.5 and 2.0 mg kg(-1)) induced dose-dependent decreases o f portal venous pressure and mean arterial pressure after intravenous infusion. For example, infusion of tetrandrine (16 mg kg(-1)) induced a maximum reduction of portal venous pressure and mean arterial pressu re approximately 1 min after the start of infusion. Portal venous pres sure decreased from baseline (12.5 mmHg) to 10.0 mmHg, and mean arteri al pressure from baseline (90 mmHg) to 80 mmHg. Heart rate decreased f rom 250 to 240 beats min(-1). At 24 mg kg(-1), tetrandrine reduced por tal venous pressure and mean arterial pressure to 20.3 +/- 2.4% and 28 .4 +/- 1.4% of baseline, respectively. Our results show that both tetr andrine and verapamil induce portal pressure reduction in portal hyper tensive animals.