Stimulation by melittin of Na+-Ca2+ exchange current in ventricular myocytes of guinea pigs.
OBJECTIVE
To study the mechanism of calcium overload induced by melittin in myocytes.


METHODS
Whole cell patch-clamp technique was applied for recording the currents.


RESULTS
Mel 0.05, 0.1 micromol/L increased the peak amplitude of I(Na) (nA) from -2.1+/-0.8 to -3.2+/-1.0 (n=7, P < 0.05) and -3.7+/-1.5 (n=7, P < 0.05) respectively at testing potential of -40 mV. Mel 0.05, 0.1, 0.2 micromol/L had no significant effect on I(Ca), but enhanced I(Na-Ca) (pA) from 53+/-21 to 427+/-256 (n=5, P < 0.05), 349+/-147 (n=5, P<0.01) and 320+/-97 (n=5, P < 0.05) respectively at a testing potential of +50 mV.


CONCLUSIONS
The stimulating effect of Mel on I(Na-Ca) rather than the effect on I(Ca) contributes to the calcium overload of myocytes.
Zhang
X M
XM
Department of Pharmacology, School of Pharmacy, Fudan University, Shanghai 200032, China.
Yang
S
S
Zhang
Y
Y
Zheng
P
P
Jiang
M H
MH
Zhou
Z N
ZN
D000818:Animals; D002469:Cell Separation; D004594:Electrophysiology; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000166:cytology; D008555:Melitten / Q000494:pharmacology*; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism; D018408:Patch-Clamp Techniques; D019831:Sodium-Calcium Exchanger / Q000187:drug effects / Q000378:metabolism*
D019831:Sodium-Calcium Exchanger; D008555:Melitten