ABSTRACT
Object To study the effects of SINI TANG (SNT) on the rat aortic rings pre-contracted by high K + and phenylephrine (Phe). Methods The effects of SNT on the aortic rings in the presence of 60 mmol/L KCl and Phe (1?10 -9 -1?10 -4 mmol/L) were observed and t heir me chanisms were studied after treatment with Propranolol (Pro, 3?10 -6 mmol/ L) and Bay K8644 (BK, 1?10 -5 mmol/L) as tool drugs. Results SNT inhibited the contraction induced by cumulative Phe and decreased the maximum tension (T max ); Pro couldn't influe nce the effects of SNT. SNT attenuated the amplitude of contractile effect of hi gh K +; BK couldn't reverse the effects of SNT. Conclusion SNT can shift the dose-response curve to the right and decrease the T max . It shows that SNT is a kind of noncompe titive antagonism. SNT decreases the effect of high K + against contraction of the artery. BK, a L-type Ca 2+ channels activator, couldn't recover the inhibition induced by SNT. The results suggest that SNT inhibit ? 1 recep tor, while calcium channel may not be involved in attenuating the effect of SNT on high K +-induced contraction.
ABSTRACT
AIM To study the effects of DIDS and furosemide on the contraction induced by phenylephrine and the endothelium-dependent relexation induced by ATP. METHODS Measurement of isometric force of rat thoracic aortae rings with and without endothelium. RESULTS DIDS(1～300 ?mol?L -1 ) and furosemide(10～320 ?mol?L -1 ) inhibited the contractile response induced by phenylephrine in a concentration-dependent manner. The inhibitory rate was different between aortic ring endothelium-intact and that endothelium-denuded. The values of IC_ 50 for DIDS were (12.0?8.0) ?mol?L -1 and (28.3?7.3) ?mol?L -1 respectively,while the values of IC_ 50 for furosemide were (17.9?6.6) ?mol?L -1 and (41.0?15.6) ?mol?L -1 respectively. DIDS(10 ?mol?L -1 ) did not chang ATP-induced vasodilative effect at the concentrations of 10 ?mol?L -1 and 100 ?mol?L -1 , but enhanced the relaxation induced by 1 mmol?L -1 ATP. Furosemide (20 ?mol?L -1 ) had no effect on the relaxation induced by ATP(10 ?mol?L -1 ), but prolonged the relaxation when the concentration of ATP added to 100 ?mol?L -1 and 1 mmol?L -1 ( P