Effects of phytoestrogen genistein on electrophysiology of human atrial fibers.

AIM: To study the electrophysiological effects of phytoestrogen genistein (GST) on human atrial fibers. METHODS: Parameters of action potential (AP) in human atrial special fibers were recorded using standard intracellular microelectrode technique. RESULTS: GST (10-100 micromol/L) decreased the velocity of diastolic (phase 4) depolarization (VDD) and rate of pacemaker firing (RPF), besides, GST (100 micromol/L) shortened the duration of 90 % repolarization of action potential (APD90). L-type Ca2+ channel agonist Bay K8644 (0.5 micromol/L) antagonized the inhibitory effects of GST on human atrial fibers, while pretreatment of the fibers with N(G)-nitro-L-arginine methyl ester (L-NAME, 1 mmol/L), an NO synthase inhibitor, failed to affect the electrophysiological effects of GST. CONCLUSION: GST exerted a negative chronotropic action and induced an accelerated repolarization of human atrial fibers. These effects were likely due to reduction in calcium influx.