B-type natriuretic peptide modulates the action potential and the L-type calcium current in adult rat heart muscle cells

Natriuretic peptides seem to be a potent regulator of cell Ca[2+] signaling in their action on the cardiovascular system. It was therefore the aim of this study to investigate the effect[s] of B-type natriuretic peptide [BNP] on the action potential and the L-type calcium current [I[cal]] in the rat left ventricular myocytes. Perforated and whole cell patch clamp technique was used to record action potential [AP] and I[cal] in current and voltage clamp mode, respectively. At the concentration tested of 10[-7] M, BNP significantly increased the action potential duration at 50% and at 90% of repolarization by 16.85% and 16.39% respectively, and the phase II slope of the AP by 52.5% ; reduced the I[cal] amplitude with a 16.17% decrease in the peak amplitude ; reduced [16.51%] the inactivation time course of current decay; increased the V[0.5] activation of the L-type calcium channel by 32.84% and decreased V[0.5] inactivation by 34.39%. These data suggest that BNP modulates cardiomyocyte function by reducing I[cal] and modifying the AP. This study may show a novel facet to evaluate the paracrine/autocrine effect of BNP on the normal heart function