ET-1 stimulates Ca2+ currents in cardiac cells.

Using the whole-cell voltage-clamp technique, endothelin (ET-1) was found to stimulate T- and L-type Ca2+ currents in a dose-dependent manner in both human and chick ventricular single cells. However, ET-1 had no effect on both the fast sodium current and the delayed outward K+ current in these cells. The effect of ET-1 on both Ca2+ currents was blocked by the ET(A) receptor antagonist BQ123. Treatment of single ventricular cells with pertussis toxin (PTX) prevented stimulation of T- and L-type calcium currents by ET-1. These results suggest that there are functional ET(A) receptors in both human and chick ventricular cells. The stimulation of both types of Ca2+ currents appears to be mediated by a PTX-sensitive G-protein.