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Electrophysiologic effects of 17#beta#--estradiol on pacemaker cells in sinoatrial nodes of rabbits

Zhou Libin, Song Lilin, Guan Yue, Guo Shumei, Yuan Fang, Zhang Yi

Department of Physiology, Hebei Medical University.Shijiazhuang 050017,Hebei

Abstract

To investigate the electrophysiological effects of 17#beta#-estradiol on pacemaker cells in sinoatrial （SA） nodes of rabbits and the underlying mechanism, intracellular microelectrode technique was used to record action potential （AP） in SA node cells of rabbits. The results showed that： （1） 17#beta#-estradiol （1, 10, 100 #mu#mol/L） not only significantly decreased the amplitude of action potential （APA） and the maximal rate of depolarization （Vmax）, but also decreased the velocity of diastolic （phase 4） depolarization （VDD） and rate of pacemaker firing （RPF） in a concentration-dependent manner. The AP duration at 50% repolarization （APD_(50)） and at 90% repolarization （APD_(90)） were prolonged. But the maximal diastolic potential （MDP） was not affected. （2） Pretreatment with tamoxifen （10 #mu#mol/ L）, an inhibitor of estrogen receptor, did not block the electrophysiological effects of 17#beta#-estradiol （10 #mu#mol/L） on SA node cells. （3） Pretreatment with N~(G)-nitro-L-arginine methyl ester （L-NAME, 100 #mu#mol/L）, a nitric oxide （NO） synthase inhibitor, completely abolished the electrophysiological effects of 17#beta#-estradiol （10#mu#mol/L） on SA node cells. The results suggest that 17#beta#-estradiol inhibits the electrophysiological activity of pacemaker cells in SA nodes of rabbits in a concentration-dependent manner possibly through a nongenomic mechanism related with NO.

Key words: 17#beta#-estradiol;Sinoatrial node;Action potential;tamoxifen;L-NAME

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Citing This Article：

Zhou Libin, Song Lilin, Guan Yue, Guo Shumei, Yuan Fang, Zhang Yi. Electrophysiologic effects of 17#beta#--estradiol on pacemaker cells in sinoatrial nodes of rabbits. Acta Physiol Sin 2007; 59 (6): 840-844 (in Chinese with English abstract).