Effect of melittin on potassium currents and action potential in ventricular myocytes of guinea pig.
OBJECTIVE
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.


CONCLUSIONS
Mel significantly increased Ik in a concentration-dependent manner which contributed to shortening of APD.
Zhang
X M
XM
Department of Pharmacology, School of Pharmacy, State Key Laboratory of Medical Neurobiology, Shanghai Medical University, Shanghai 200032, China.
Yang
S
S
He
X J
XJ
Zheng
P
P
Jiang
M H
MH
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002469:Cell Separation; D006168:Guinea Pigs; D008555:Melitten / Q000494:pharmacology*; D009206:Myocardium / Q000166:cytology*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects*; D016276:Ventricular Function
D015221:Potassium Channels; D008555:Melitten