Modification of Ca(2+)-sensitivity of Ca(2+)-activated Cl- channel by vasopressin and cholera toxin.

The apical membrane of renal epithelium (A6) had a Ca(2+)-activated, outwardly rectified chloride channel with the single channel conductance of 3 pS for outward current and 0.5 pS for inward current. The outward rectification was dependent on the cytosolic Ca2+ concentration. Vasopressin (arginine vasopressin, AVP) and cholera toxin (CTX) increased the single channel conductance for inward current through an increase in the Ca(2+)-sensitivity about 100-fold.