THE ENDOCARDIAL ENDOTHELIUM - FUNCTION AND ELECTROPHYSIOLOGY

Basic electrophysiological properties of cultured endocardial endothel ial (EE) cells from the porcine right ventricle were studied by the co nventional whole-cell patch-clamp technique. In isotonic conditions, t he major membrane current in resting EE cells was an inwardly rectifyi ng K-current (I-K) responsible for the negative value of the resting p otential (-50 to -70mV). Outwardly directed currents at positive clamp potentials were small. In hypotonic conditions (hypertonic pipette so lution), cells depolarized and an outwardly rectifying Cl-current was activated. The volume-activated current was inactivated by returning t o isotonic conditions and was inhibited by DIDS (4,4'-diisothiocyanost ilbene-2,2' disulfonic acid, 100-300 mu M) or flufenamic acid 50-100 m u M. A possible role of the Cl-current in EE cells is discussed.