Aim: To examine the effects of melittin (Mel), the major component of bee venom, on delayed rectifier K+ current (Ik), inward rectifier K+ current (Ikl) and action potential (AP) in guinea pig ventricular myocytes.
Methods: Ik, Ikl, and AP were recorded using the whole-cell patch-clamp technique.
Results: The action potential duration (APD) was shortened by Mel in a concentration-dependent manner. Mel 0.05, 0.1, 0.2 mumol.L-1 shortened APD50 from (520 +/- 55) to (459 +/- 91) (n = 5, P > 0.05), (385 +/- 102) (n = 5, P < 0.01), and (281 +/- 81) ms (n = 5, P < 0.01), respectively; and APD90 from (613 +/- 96) to (536 +/- 93) (n = 5, P > 0.05), (467 +/- 96) ms (n = 5, P < 0.01), and (354 +/- 95) ms (n = 5, P < 0.01), respectively. Mel increased the amplitude of Ik also in a concentration-dependent manner. Mel 0.05, 0.1, 0.2 mumol.L-1 increased Ik from (295 +/- 109) to (371 +/- 142) (n = 5, P < 0.05), (467 +/- 180) (n = 5, P < 0.05), (552 +/- 248) pA (n = 5, P < 0.05), respectively at testing potential of + 40 mV. But no significant effect of Mel on Ikl was observed at these concentrations.
Conclusion: Mel significantly increased Ik in a concentration-dependent manner which contributed to shortening of APD.