[Inhibition of Na+/Ca2+ exchange by tetrapeptide FMRFa in intact rat ventricular myocytes].
OBJECTIVE
To study the effects of Phe-Met-Arg-Phe-NH2(FMRFa) on Na+/Ca2+ exchange and its specificity for Na+/Ca2+ exchange in rat ventricular myocytes.


METHODS
Na+/Ca2+ exchange current and other currents of ion channels were measured using whole cell voltage clamp techniques.


RESULTS
A dose-related inhibition of tetrapeptide FMRFa on Na+/Ca2+ exchange was observed in rat ventricular myocytes. Inward and outward INa+/Ca2+ were inhibited by 60.1% and 56.5%, respectively, at highest concentration (100 mumol.L-1) and its IC50 were 20 mumol.L-1 and 34 mumol.L-1 in inward and outward INa+/Ca2+, respectively. Inward and outward INa+/Ca2+ were inhibited 38.7% and 34.9%, respectively, at FMRFa 5 mumol.L-1. FMRFa 5 mumol.L-1 and 20 mumol.L-1 did not affect L-type calcium current, sodium current, transient outward current and inward rectifier potassium current.


CONCLUSIONS
These data indicate that FMRFa is a specific inhibitor of Na+/Ca2+ exchange in intact rat ventricular myocytes.
Han
Q H
QH
Department of Physiology, Shanxi Medical University, Taiyuan 030001, China.
Wu
D M
DM
Lu
J Y
JY
Wu
B W
BW
D000818:Animals; D019835:FMRFamide / Q000494:pharmacology*; D005260:Female; D006352:Heart Ventricles; D008297:Male; D032383:Myocytes, Cardiac / Q000166:cytology / Q000502:physiology*; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar; D019831:Sodium-Calcium Exchanger / Q000187:drug effects*
D019831:Sodium-Calcium Exchanger; D019835:FMRFamide