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Electrophysiological effects of phytoestrogen genistein on sporntx neous activity of rabbit atrioverntricular nodecells

Cheng Yanping, Ma Tao, HE Rui- Rong

Department of Physiology，Institute of Basic Medicine，Hebei Medical Univesity，Shijiazhuang 050017

Abstract

The purpose of this study was to determine the elect rophysiological effects of genistein(GS T) on spontaneous activity of atrioventricular(A均node and the underlying mechanisms).Action potentials in AV node cells were recorded
using intracellular microelectrode technique .GST not only reduced the amplitude of action potential(AP A)，maximal rate of depolarization(V _j，velocity of diastolic(phase 4) depolarization(V D D)，and rate of spontaneous firing(RS F)，but also prolonged 90%duration of action potential(AP马。)in a concentratiorr dependent manner.The effects of GS T(50 umol/ L)
could be blocked completely by pretreatment with Bay K8644(0. 25 umol/ L)，an agonist of L -type calcium channel.Pretreatment with N'-nitro- L-arginine methyl ester(L-NAME，0.5 m mol/ L)，a nitric oxide(NO) synthase inhibitor，did
not affect the effects of GST on AV node cells .Elevation of Cat+concentration(5 m mol/ L) in superfusate antagonized the effects of GS T(50 umol/ L).These results suggest that GST exerted a negative elect rophysiological effects of spontaneous activity of AV node cells in rabbits .These effects were likely due to reduction in calcium influx，but had no association with NO release.

Key words: Phytoestrogen;genistein;Atrioventricular node;calcium currents

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Citing This Article：

Cheng Yanping, Ma Tao, HE Rui- Rong. Electrophysiological effects of phytoestrogen genistein on sporntx neous activity of rabbit atrioverntricular nodecells . Acta Physiol Sin 2003; 55 (1): (in Chinese with English abstract).