The peptide "FRCRCFa", dialysed intracellularly, inhibits the Na/Ca exchange in rabbit ventricular myocytes with high affinity.
We investigated the effect in rabbit ventricular myocytes of "FRCRCFa", a newly developed peptide inhibitor of the Na/Ca exchange. Myocytes were whole-cell patch clamped and experiments were carried out at 36 degrees C. The Na/Ca exchange was measured selectively, by blocking interfering ion channel currents and the Na/K pump, as the membrane current which could be inhibited by 5 mM nickel (Ni; a known blocker of the Na/Ca exchange). Increasing concentrations of FRCRCFa dialysed into the cell from the patch-pipette inhibited the Na/Ca exchange current. The dose/response curve could be fitted by a function for co-operative ligand binding, which predicted a KD for FRCRCFa-mediated inhibition of 22.7 +/- 3.7 nM, with a Hill coefficient of 0.61 +/- 0.06. Pipette FRCRCFa concentrations of 1 micro;M and above were sufficient to cause complete inhibition of Na/Ca exchange current. The inhibitory effect of FRCRCFa was independent of membrane potential and relatively selective: 10 micro;M FRCRCFa dialysed into the cell had no effect on the L-type Ca current and delayed rectifier and inward rectifier K currents. Thus FRCRCFa appears to be a potent and relatively selective inhibitor of the Na/Ca exchange in intact cardiac myocytes, and may be of value for studies of the Na/Ca exchange.
Hobai
I A
IA
Department of Physiology, School of Medical Sciences, University Walk, University of Bristol, Bristol BS8 1TD, UK.
Khananshvili
D
D
Levi
A J
AJ
D000818:Animals; D004305:Dose-Response Relationship, Drug; D006352:Heart Ventricles / Q000187:drug effects*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects*; D010455:Peptides / Q000494:pharmacology*; D011817:Rabbits; D000254:Sodium-Potassium-Exchanging ATPase / Q000187:drug effects*
D010455:Peptides; D000254:Sodium-Potassium-Exchanging ATPase