[Electrophysiological effects of phytoestrogen genistein on guinea pig papillary muscles].
The cardiac electrophysiological effects of genistein (GST) were examined in guinea pig papillary muscle using intracellular microelectrode technique. The results obtained are as follows. (1) Duration of action potential (APD) in normal papillary muscles was decreased by GST (10 100 micromol/L) in a concentration-dependent manner. (2) In partially depolarized papillary muscles, 50 micromol/L GST not only reduced APD, but also decreased the amplitude of action potential, overshoot and maximal velocity of phase 0 depolarization. (3) Pretreatment with N( )-nitro-L-arginine (L-NNA, 5 mmol/L) failed to affect the above effects of GST (50 micromol/L)on papillary muscles. (4) 17beta-estradiol (E(2), 5 micromol/L) or GST (10 micromol/L) alone did not affect action potential, while GST combined with E(2) at the same doses shortened APD significantly. All these results indicate that the effects of GST on papillary muscles are likely due to a decrease of calcium inflow which is not mediated by NO and that GST has a facilitative or synergetic action with E(2).
Ma
Tao
T
Department of Physiology, Institute of Basic Medicine, Hebei Medical University, Shijiazhuang 050017, syho@hebmu.edu.cn
Fan
Zhen-Zhong
ZZ
He
Rui-Rong
RR
D000200:Action Potentials / Q000187:drug effects; D000376:Agmatine / Q000494:pharmacology; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004594:Electrophysiology; D004958:Estradiol / Q000494:pharmacology; D004968:Estrogens, Non-Steroidal / Q000494:pharmacology*; D005260:Female; D019833:Genistein / Q000494:pharmacology*; D006168:Guinea Pigs; D007529:Isoflavones; D008297:Male; D010210:Papillary Muscles / Q000187:drug effects / Q000502:physiology*; D048789:Phytoestrogens; D028321:Plant Preparations
D004968:Estrogens, Non-Steroidal; D007529:Isoflavones; D048789:Phytoestrogens; D028321:Plant Preparations; D004958:Estradiol; D000376:Agmatine; D019833:Genistein