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[Inhibition of Na+/Ca2+ exchange by tetrapeptide FMRFa in intact rat ventricular myocytes]
1Department of Physiology, Shanxi Medical University, Taiyuan 030001, China.
Aim:
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.
Conclusion:
These data indicate that FMRFa is a specific inhibitor of Na+/Ca2+ exchange in intact rat ventricular myocytes.
