Prostaglandin E2 inhibits Na+-K+-ATPase activity in the inner medullary collecting duct

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Abstract
Prostaglandin E2 (PGE2) is natriuretic and inhibits collecting duct sodium transport by poorly defined mechanisms. To determine the mechanism of this inhibition, we have studied the effect of PGE2 on ouabain-sensitive (transport-dependent) oxygen consumption (QO2), ouabain-sensitive 86Rb+ uptake and ouabain-sensitive ATPase activity in fresh suspensions of rabbit inner medullary collecting duct cells, as well as Na+-K+-ATPase activity in inner medullary membranes. PGE2 (10-5 M) reduced total QO2 by 21.6 .+-. 2.3% (mean .+-. SE) and reduced the ouabain-sensitive component of QO2 in IMCD cells. PGE2 failed to inhibit QO2 in the absence of sodium or in the presence of ouabain and blunted the increase in QO2 in response to amphotericin B. These results suggested that PGE2 inhibited Na+-K+-ATPase activity. Inhibition of pump activity was confirmed by measurements of 86Rb+ uptake: PGE2 (10-5 M) reduced ouabain-sensitive 86Rb+ uptake by 57% at 10 s without altering equilibrium uptake. Furthermore, PGE2 (10-6 M) reduced ouabain-sensitive ATPase activity by 46% in permeabilized inner medullary collecting duct cells. PGF2.alpha. (10-5 M) did not significantly alter QO2. 86Rb+ uptake, or Na+-K+-ATPase activity. These results demonstrate that PGE2 inhibits inner medullary collecting duct Na+-K+-ATPase activity and suggest a role for this inhibition in the natriuretic effect of PGE2.

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