RESUMO
Aim To study the effect of genistein on contractility of isolated papillary muscles in guinea pig and its mechanisms.Methods Isolated guinea pig papillary muscles were suspended in organ baths containing KH solution,and the effect of genistein on contractility of myocardium was observed after an equilibration period.Results Genistein and isoprenaline hydrochloride showed positive inotropic effects on contractility of myocardium in a dose-dependent manner(1～100 ?mol?L~(-1)) Propranolol(1 ?mol?L~(-1)) and verapamil hydrochloride(0.5 ?mol?L~(-1)) attenuated the positive inotropic effect of isoprenaline hydrochloride(2 ?mol?L~(-1)),but did not change the effect of genistein(100 ?mol?L~(-1)).Furthermore,the enhancement of the contractility induced by elevation of extracellular Ca~(2+) concentration in papillary muscles did not show any change after pretreatment with genistein(1,10 ?mol?L~(-1)).Finally,the positive inotropic effect of genistein was attenuated partially by tamoxifen(1 ?mol?L~(-1)),however,was not influenced by sodium orthovanadate(1 ?mol?L~(-1)).Conclusions Genistein has the positive inotropic effect on guinea pig papillary muscles,which is not related to the activation of Ca~(2+) channel on cell membrane,? adrenoceptor and tyrosine kinase pathway,but this effect may involve in uptake and utilization of sarcoplasmic reticulum Ca~(2+).