INHIBITION OF APICAL NA+ CHANNELS IN RABBIT CORTICAL COLLECTING TUBULES BY BASOLATERAL PROSTAGLANDIN-E2 IS MODULATED BY PROTEIN-KINASE-C

We used the cell-attached patch clamp technique to investigate the interaction of exogenous prostaglandins (PG), intracellular [Ca2+]i, and protein kinase C (PKC) on the high selectivity, 4 pS Na+ channel found in the principal cell apical membrane of rabbit cortical collecting tubule (CCT) cultures grown on collagen supports with 1.5 muM aldosterone. Application of 0.5 muM PGE2 to the basolateral membrane decreased mean NP. (number of channels times the open probability) for apical Na+ channels by 46.5% (n = 9). There was no consistent change in NP(o) after apical 0.5 muM PGE2 (n = 12) or after apical or basolateral 0.5 muM PGF2alpha (n = 8). Release of [Ca2+]i stores with 0.25 muM thapsigargin (n = 7), or activation of apical membrane PKC with apical 0.1 muM 4beta-phorbol-12-myristate-13-acetate (n = 5) or 10 muM 1-oleyl-2-acetylglycerol (n = 4) also decreased NP(o). Depletion of [Ca2+]i stores (0.25 muM thapsigargin pretreatment) (n = 7) or inhibition of apical PKC (100 muM D-sphingosine pretreatment) (n = 8) abolished the inhibitory effects of basolateral PGE2. Conclusions: (a) apical Na+ transport in rabbit CCT principal cells is modulated by basolateral PGE2; (b) the mechanism involves release of IP3-sensitive, [Ca2+]i stores; and (c) Ca2+-dependent activation of apical membrane PKC, which then inhibits apical Na+ channel.