CARBACHOL-INDUCED POTASSIUM RELEASE IN RAT PAROTID ACINI - COMPARISONOF THE ROLES OF CYTOSOLIC CA2-KINASE-C( AND PROTEIN)

Carbachol (CCh) stimulated K+ release from rat parotid acini. Treatmen t with the intracellular Ca2+ antagonist 8-(N,N-diethylamino)octyl-3,4 ,5-trimethoxybenzoate (TMB-8) or the intracellular Ca2+ chelator ,2-bi s(O-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) strongly su ppressed the CCh-induced K+ release. Combined addition of the Ca2+ ion ophore ionomycin and the microsomal Ca2+-ATPase inhibitor thapsigargin caused a rapid increase in cytosolic Ca2+ concentration ([Ca2+](i)) a nd resulted in a marked release of K+. In the absence of extracellular Ca2+, CCh or a combination of ionomycin and thapsigargin caused a tra nsient release of K+ which correlated well with the transient change i n [Ca2+](i). On the other hand, phorbol 12-myristate 13-acetate (PMA) did not potentiate the CCh-induced K+ release, although the CCh-induce d amylase release was significantly enhanced in the presence of PMA. S taurosporine, a protein kinase C-inhibitor, did not inhibit the CCh-in duced K+ release, which was in contrast with its inhibitory effect on amylase release. These results suggest that the K+ release from rat pa rotid acini induced by CCh stimulation is mediated by a rapid increase in [Ca2+](i) but is not associated with activation of protein kinase C. This signal pathway is different from that for amylase release wher e activation of protein kinase C plays an important role.