Regulation of volume-sensitive outwardly rectifying anion channels in pulmonary arterial smooth muscle cells by PKC

We tested the possible role of endogenous protein kinase C (PKC) in the regulation of native volume-sensitive organic osmolyte and anion channels (VSOACs) in acutely dispersed canine pulmonary artery smooth muscle cells (PASMC). Hypotonic cell swelling activated native volume-regulated Cl- currents (I-Cl.vol) which could be reversed by exposure to phorbol 12,13-dibutyrate (0.1 muM) or by hypertonic cell shrinkage. Under isotonic conditions, calphostin C (0.1 muM) or Ro-31-8425 (0.1 muM), inhibitors of both conventional and novel PKC isozymes, significantly activated I-Cl.vol and prevented further modulation by subsequent hypotonic cell swelling. Bisindolylmaleimide (0.1 muM), a selective conventional PKC inhibitor, was without effect. Dialyzing acutely dispersed and cultured PASMC with epsilonV1-2 (10 muM), a translocation inhibitory peptide derived from the V1 region of epsilonPKC, activated I-Cl.vol under isotonic conditions and prevented further modulation by cell volume changes. Dialyzing PASMC with betaC2-2 (10 muM), a translocation inhibitory peptide derived from the C2 region of betaPKC, had no detectable effect. Immunohistochemistry in cultured canine PASMC verified that hypotonic cell swelling is accompanied by translocation of epsilonPKC from the vicinity of the membrane to cytoplasmic and perinuclear locations. These data suggest that membrane-bound epsilonPKC controls the activation state of native VSOACs in canine PASMC under isotonic and anisotonic conditions.