Effects of calcium on prostaglandin E2 synthesis by rat inner medullary slices

Abstract

The effect of Ca2+ on synthesis of prostaglandin E2 (PGE2) was examined using inner medullary slices of rat kidney. Medullary PGE2 production was reduced by 60% when slices were incubated in Ca2+-free medium containing EGTA [ethylene glycol bis tetraacetic acid]. It was necessary to use Ca2+-free medium for the 20 min preincubation and the final 15 min incubation. The reduced PGE2 synthesis observed with Ca2+-free medium containing EGTA could be reversed by adding Ca2+ but not Mg2+ during the final incubation. Arachidonic acid also overcame the inhibition induced by Ca2: deprivation. Increases in prostaglandin production by Ca2+ or arachidonic acid were blocked by meclofenamic acid, a prostaglandin synthetase inhibitor. Addition of the divalent ionophore A23187 (1.9 .times. 10-5 M) during preincubation did not alter PGE2 synthesis in Ca2+-free medium. This ionophore potentiated increases in PGE2 synthesis observed with Ca2+ addition. Mg2+ remained ineffective wth or without preincubation of slices with A23187. Verapamil and tetracaine, Ca2+ transport blockers, blocked both increases in PGE2 seen with Ca2+ addition and A23187 potentiation of the Ca effect. PGE2 production by medullary slices is apparently Ca2+ dependent. Ca2+ transport or intracellular Ca2+ could be important in PGE2 synthesis.