Interactions among prostaglandin E2, antidiuretic hormone, and cyclic adenosine monophosphate in modulating Cl- absorption in single mouse medullary thick ascending limbs of Henle.

This paper describes the inhibitory effect of prostaglandin E2 (PGE2) on antidiuretic hormone (ADH)-stimulated net Cl- absorption and spontaneous transepithelial voltage (Ve) in single medullary thick ascending limbs of Henle (TALH, thick ascending limb; mTALH, medullary segment; cTALH, cortical segment) obtained from mouse kidney. The experimental data indicate that PGE2 reduced the ADH-dependent values of net Cl- absorption (JnetCl, eq cm-2 s-1) and Ve (mV) in a dose-dependent manner; that increasing concentrations of peritubular ADH reversed the PGE2-mediated reductions in the ADH-dependent moiety of Ve in the mouse mTALH; that PGE2 had no effect on cyclic AMP-stimulated increments in Ve in the mouse mTALH; and that PGE2 had no effect on Ve in the cTALH, where Ve is unaffected either by ADH or by cyclic AMP. These effects might be obtained because of a direct competition between ADH and PGE2 for receptor binding on basolateral membranes. Alternatively, PGE2 might have reduced the affinities between ADH-receptor units and a component(s) of the series of processes leading to adenyl cyclase activation. The latter argument requires that basolateral membranes of the mouse mTALH exhibit receptor reserve, i.e., at the minimum concentration of ADH required to enhance Ve and JnetCl maximally, a fraction of basolateral membrane ADH receptors were unoccupied. According to this view, increasing peritubular ADH concentrations might reverse the PGE2-mediated reduction in ADH-dependent salt transport by increasing the number of basolateral membrane receptors occupied by ADH.