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 microM aldosterone. Application of 0.5 microM PGE2 to the basolateral membrane decreased mean NP0 (number of channels times the open probability) for apical Na+ channels by 46.5% (n = 9). There was no consistent change in NP0 after apical 0.5 microM PGE2 (n = 12) or after apical or basolateral 0.5 microM PGF2 alpha (n = 8). Release of [Ca2+]i stores with 0.25 microM thapsigargin (n = 7), or activation of apical membrane PKC with apical 0.1 microM 4 beta-phorbol-12-myristate-13-acetate (n = 5) or 10 microM 1-oleyl-2-acetylglycerol (n = 4) also decreased NP0. Depletion of [Ca2+]i stores (0.25 microM thapsigargin pretreatment) (n = 7) or inhibition of apical PKC (100 microM 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) Ca(2+)-dependent activation of apical membrane PKC, which then inhibits apical Na+ channels.
B N Ling, K E Kokko, D C Eaton