Prostaglandin E2 stimulates sodium reabsorption in MDCK C7 cells, a renal collecting duct principal cell model

Abstract

We examined the direct epithelial effects of the major product of arachidonic acid metabolism in the kidney, prostaglandin E₂ (PGE₂), on ion transport and signal transduction in the hormone-sensitive Madin–Darby canine kidney (MDCK) C7 subclone as a model of renal collecting duct principal cells. MDCK C7 cells were grown on microporous permeable filter supports and mounted in Ussing-type chambers. Reverse transcriptase (RT)-PCR and sequencing were used to determine E-prostanoid (EP) receptor expression. Basolateral and, about 14-fold less potent, apical addition of PGE₂ increased short-circuit current (I_sc) in a concentration-dependent manner. This ion transport was biphasic with a rapid peak not detectable under chloride-free conditions. The remaining, stably elevated current was unaffected by furosemide, hydrochlorothiazide, ethylisopropanol amiloride, and 5-nitro-2-(3-phenyl-propyl-amino)benzoic acid (NPPB). In contrast, apical amiloride (10 μM) significantly decreased I_sc, indicating sodium reabsorption. The effect of PGE₂ was attenuated in the presence of vasopressin. Agonists acting by cAMP elevation like dibutyryl-cAMP and theophylline also induced an amiloride-sensitive ion transport with similar kinetics as PGE₂. Moreover, PGE₂ rapidly increased intracellular cAMP levels. RT-PCR demonstrated mRNA expression of the epithelial sodium channel (ENaC), and of the EP2 receptor in MDCK C7 cells. Accordingly, EP2 receptor agonist butaprost mimicked PGE₂ epithelial action. In conclusion, PGE₂ induces amiloride-sensitive sodium reabsorption in MDCK C7 monolayers. This ion transport is most likely mediated by EP2 receptor activation leading to increased intracellular cAMP levels. Therefore, PGE₂ might also contribute to Na⁺ reabsorption in the mammalian collecting duct.