Independent Effects of Bradykinin on Adenosine 3′,5′-Monophosphate and Prostaglandin E2Metabolism by Rabbit Renal Medulla*

Bradykinin-stimulated increases in renal prostaglandin (PG) synthesis are thought to result in subsequent increases in cAMP content. This study assesses the relationship between bradykinin-stimulated increases in PGE2 and cAMP syntheses in renal inner medullary slices. Bradykinin-mediated increases in cAMP (2 min) preceded those in PGE2 (5 min) synthesis. Forskolin, an activator of adenylate cyclase, increased cAMP, while 2',5'-dideoxyadenosine, an adenylate cyclase inhibitor, reduced cAMP. However, neither agent altered bradykinin-stimulated PGE2 synthesis. Aspirin decreased basal and abolished bradykinin-stimulated PGE2 production, but did not alter bradykinin-induced increases in cAMP content. Maximal stimulatory concentrations of 1-methyl-3-isobutylxanthine, a cyclic nucleotide phosphodiesterase inhibitor, and bradykinin were additive in their capacity to increase inner medullary cAMP content. These results suggest that 1-methyl-3-isobutylxanthine and bradykinin increase cAMP by separate mechanisms and that bradykinin increases inner medullary cAMP by a direct effect on the production of that cyclic nucleotide. Bradykinin-mediated increases in cAMP and PGE2 syntheses by renal medullary slices are independent effects of this renally acting hormone.