Stimulation by melittin of Na+-Ca2+ exchange current in ventricular myocytes of guinea pigs

AIM: To study the mechanism of calcium overload induced by melittin in myoc ytes. METHODS: Whole-cell patch-clamp technique was applied for recording t he currents. RESULTS: Mel 0.05, 0.1 mu mol/L increased the peak amplitude o f I-Na(nA) from -2.1+/-0.8 to -3.2+/-1.0 (n = 7, P < 0.05) and -3.1+/-1.5 ( n = 7, P < 0.05) respectively at testing potential of -40 mV. Mel 0.05, 0.1 , 0.2 mu mol/L had no significant effect on I-Ca, but enhanced INa-Ca(pA) f rom 53 +/- 21 to 427+/-256 (n = 5, P < 0.05), 349 +/- 147 (n = 5, P < 0.01) and 320 +/- 91 (n = 5, P < 0.05) respectively at a testing potential of 50 mV. CONCLUSION: The stimulating effect of Mel on INa-Ca rather than the effect on Ica contributes to the calcium overload of myocytes.