INDUCTION OF ALKALINIZATION IN CULTURED RENAL-CELLS (MDCK LINE) BY PROSTAGLANDIN E(2)

The effect of prostaglandin E(2) (PGE(2)), on the intracellular pH (pH i) in BCECF-loaded Madin Darby Canine Kidney (MDCK) cells was investig ated. PGE, elevated the pHi: Under resting conditions, pHi of MDCK cel ls suspended in PBS at pH 7.4 was 7.11 +/- 0.08; PGE(2) in creased pHi with an EC(50) of 0.16 mu M. PGF(2 alpha) elicited a similar response to PGE(2), with an EC(50) of 0.24 mu M. Amiloride (0.4 mM) reversed t he response to PGE(2) (control 7.28 +/- 0.05; PGE(2) 7.26 +/- 0.05; af ter amiloride 7.28 +/- 0.05). In MDCK cells exposed to a Na+-free solu tion, alkalinization induced by this eicosanoid was blocked (Ringer-ch oline 7.16 +/- 0.03; PGE(2) 7.16 +/- 0.02). PGE(2) increased by 100% t he rate of recovery after an acidification guise with ammonium chlorid e. In the presence of Ringer-HCO3- (pH 7.4), there was a delay in the maximal response to this prostaglandin (PBS 2.2 +/- 0.27, Ringer-bicar bonate 3.4 +/- 0.55 min) and the pHi increment was less marked than in PBS (0.09 pH units in HCO3- versus 0.16 pH units in PBS; P < 0.001). This effect of PGE(2) was not blocked by 4,4'-diisothiocyanatostilbene -2,2'-disulfonic acid (1.0 mM). PMA (100 nM), activator of protein kin ase C, mimicked the response to PGE(2), suggesting the participation o f this kinase on the effect of the prostanoid. As expected, two inhibi tors of protein kinase C, stamosporine and sphingosine, abolished the response to PGE(2). Staurosporine (0.10 mu M), an inhibitor of protein kinase C, blocked the response to PGE(2) (control 7.02 +/- 0.04;