PGE₂ inhibits Na-K-ATPase activity and ouabain binding in MDCK cells

In the present study we report on a direct effect of prostaglandin E₂ (PGE₂) on ouabain binding and Na-K-adenosinetriphosphatase (Na-K-ATPase) activity in a clone of Madin-Darby canine kidney cells, a renal cell line with collecting duct properties. Incubation of the cells with low concentrations (pM) of PGE₂ produced a concomitant reduction of ∼50% in the activity of Na-K-ATPase in the cell homogenate and in ouabain binding to the intact cells (half-maximal inhibition of ∼0.1 pM). The inhibition was apparent within 10 min of preincubation of the cells with PGE₂. Scatchard analysis of the binding demonstrated that the treatment with PGE₂ reduced the number of ouabain binding sites without a change in the dissociation constant. PGE₁ and PGF_2α (10 nM) did not affect ouabain binding or Na-K-ATPase activity. The fast, potent, and specific effect of PGE₂ suggests that the diuretic/natriuretic effect of prostaglandins of the E series in the collecting tubule, in addition to the interference with the activity of arginine vasopressin, may result from a direct reduction in the number of the Na-K-ATPase active units, via a prostaglandin receptor.