PGE2 inhibits water permeability at a post-cAMP site in rat terminal inner medullary collecting duct

To assess sites and mechanism of action of prostaglandin E2 (PGE2) on water permeability (PF), we determined PGE2 effects on antidiuretic hormone (ADH)- and adenosine 3',5'-cyclic monophosphate (cAMP)-stimulated PF in rat terminal inner medullary collecting ducts perfused in vitro. PGE2 (10(-7) M) reversibly inhibited ADH-stimulated PF (1.131 +/- 192 to 532 +/- 208 microns/s). In contrast to that observed in rabbit, PGE2 also inhibited an established PF response to the exogenous cAMP analogue 8-p-(chlorophenylthio)-cAMP (696 +/- 107 to 399 +/- 99 microns/s). PGE2 alone had no effect on PF. The protein kinase C inhibitor staurosporine (10(-8) M) blocked PGE2-mediated inhibition of cAMP-stimulated PF. PGE2 caused a rapid spikelike increase in intracellular calcium [( Ca2+]i) followed by a stable elevation above basal values. Only the latter effect was abolished in a zero calcium bath. Neither staurosporine nor cAMP altered the [Ca2+]i response. These studies are the first to demonstrate PGE2-mediated inhibition of an established PF response to cAMP independent of changes in intracellular cAMP. The pattern of [Ca2+]i release and sensitivity to staurosporine suggests that this effect is mediated via signaling through phospholipase C. The results underscore the importance of species differences, axial heterogeneity, and/or in vivo conditioning for functional expression of cellular signaling pathways.