Control of prostaglandin E2 synthesis in cultured rat inner medullary collecting tubule cells: the role of calcium.

We investigated the role of calcium in basal, ionophore- and hormone-stimulated prostaglandin E2 (PGE2) production by rat inner medullary collecting tubule cells. Basal PGE2 production is significantly decreased in the absence of calcium (4.49 +/- 0.79 vs. 19.99 +/- 3.47 pg/micrograms protein/h, p less than 0.001). No further increment is seen at 4 mM calcium. The ability of the calcium ionophore A23187 to stimulate PG production is proportional to the amount of calcium present in the extracellular space. Bradykinin is a potent stimulus to PG production even in the virtual absence of calcium while arginine vasopressin has only a modest effect. Neither bradykinin nor arginine vasopressin exhibit any further PG stimulation at 1 mM calcium; both bradykinin and arginine vasopressin increase PGE2 production significantly when calcium is increased to a supraphysiologic level. The data suggests an important role for intracellular rather than extracellular calcium in the control of PG production. Bradykinin but not vasopressin display significant calcium-independent stimulatory effects on PG synthesis.