Inhibitory effects of estradiol on inward rectifier and delayed rectifier K+ currents in guinea pig ventricular myocytes

AIM: To study the effects of estradiol (Est) on inward rectifier K+ (I-Kl) and delayed rectifier K+ (I-K) channels in isolated guinea pig ventricular myocytes. METHODS: Using whole cell patch-clamp recording techniques. RESUL TS: Est 10 mu mol . L-1 and 100 mu mol . L-1 decreased the action potential duration, APD(50), from (414 +/- 71) ms to (330 +/- 75) ms and (229 +/- 67 ) ms (n = 7 cells of 7 guinea pigs, P < 0.05), respectively. Est 100 mu mol . . L-1 also decreased APD(90) from (587 +/- 60) ms to (418 +/- 79) ms (n = 7, P <0.05). Est inhibited I-K tail current (I-K tail) concentration-depen dently. I-K tail was depressed 53% (n = 5, P < 0.05) at 10 mu mol . L-1 and 80% (n = 5, P <0.01) at 100 mu mol . L-1 compared with control. Est greate r than or equal to 10 mu mol . L-1 blocked I-Kl. The maximal inhibition of inward current of I-Kl occurred at - 100 mV test potential was 49% (n = 5, P <0.01) and outward current of I-Kl at - 40 mV was 72% (n = 5, P < 0.01). The reverse potential shifted negatively, from -70 to -76 mV. CONCLUSION: E st possessed blocking effects on both I-Kl and I-K channels in guinea pig v entricular myocytes.