REGULATION OF EPITHELIAL NA-KINASE-C IS TISSUE-SPECIFIC( PERMEABILITYBY PROTEIN)

Protein kinase C (PKC) is a major regulator of a broad range of cellul ar functions. Activation of PKC has been reported to stimulate Na+ tra nsport across frog skin epithelium by increasing the apical Na+ permea bility. This positive natriferic response has not been observed with o ther epithelial preparations, and could reflect the specific experimen tal conditions of different laboratories, or species or organ specific ity of the response to PKC. In the present study, measurements were co nducted with skins and urinary bladders from the same animals of two d ifferent species. The PKC activator TPA uniformly increased the transe pithelial Na+ transport (measured as amiloride-sensitive short-circuit current, I-SC across skins from Rana temporaria and Bufo marinus, and inhibited I-SC across bladders from the same animals. Inhibitors of P KC (staurosporine, H-7 and chelerythrine) partially blocked the TPA-in duced stimulation of I-SC across frog skin. The specificity of the PKC response by amphibian skin could have reflected an induction of moult ing, similar to that observed with aldosterone. However, light microgr aphs of paired areas of frog skin revealed no evidence of the putative moulting. Separation of stratum corneum from the underlying stratum g ranulosum could be detected following application of aldosterone. We c onclude that the effect of PKC on epithelial Na+ channels is organ, an d not species specific. The stimulation of Na+ permeability in amphibi an skin does not arise from sloughing of the stratum corneum. These ob servations are consistent with the hypothesis that the natriferic acti on arises from the calcium-independent isozyme of PKC previously detec ted in frog skin.