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 Ca2+ signalling 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 1639% 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 V0.5 activation of the L-type calcium channel by 32.84% and decreased V0.5 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.