Effects of phytoestrogen genistein on delayed after depolarization and triggered activity induced by ouabain in guinea pig papillary muscles.
The purpose of this study was to investigate the effects of phytoestrogen genistein (GST) on delayed after depolarization (DAD) and triggered activity (TA) induced by ouabain in guinea pig papillary muscles. Action potentials (APs) were recorded from the guinea pig papillary muscles with standard glass microelectrode technique. The results are as follows: (1) DAD and TA induced by ouabain (1 micromol/L) were markedly inhibited by pretreatment with GST (10, 50, 100 micromol/L) in a concentration-dependent manner. (2) NG-nitro-L-arginine methyl ester (L-NAME, 1 mmol/L), an NO synthase inhibitor, failed to affect the above effects of GST. (3) 5 micromol/L 17beta-estradiol (E2) or 10 micromol/L GST alone showed no effects on DAD and TA, whereas GST combined with E(2) at the same doses exerted significant inhibitory effects on DAD and TA. Since GST is known to reduce the calcium influx, it is suggested that GST might have antiarrhythmic effects, possibly by reducing calcium influx. The antiarrhythmic effects of GST may contribute to its cardioprotective action.
Ma
Tao
T
Department of Physiology, Institute of Basic Medicine, Hebei Medical University, Shijiazhuang, China.
He
Rui-Rong
RR
Wang
Chuan
C
D000200:Action Potentials / Q000187:drug effects*; D000818:Animals; D019833:Genistein / Q000494:pharmacology*; D006168:Guinea Pigs; D008297:Male; D009467:Neuromuscular Depolarizing Agents / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D010210:Papillary Muscles / Q000187:drug effects* / Q000502:physiology; D048789:Phytoestrogens / Q000494:pharmacology*
D009467:Neuromuscular Depolarizing Agents; D048789:Phytoestrogens; D010042:Ouabain; D019833:Genistein