ET-1 STIMULATES CA2-CELLS( CURRENTS IN CARDIAC)

Using the whole-cell voltage-clamp technique, endothelin (ET-1) was fo und to stimulate T- and L-type Ca2+ currents in a dose-dependent manne r 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+ c urrent in these cells. The effect of ET-1 on both Ca2+ currents was bl ocked by the ET(A) receptor antagonist BQ123. Treatment of single vent ricular cells with pertussis toxin (PTX) prevented stimulation of T- a nd L-type calcium currents by ET-1. These results suggest that there a re functional ET(A) receptors in both human and chick ventricular cell s. The stimulation of both types of Ca2+ currents appears to be mediat ed by a PTX-sensitive G-protein.