Expression of prostaglandin E receptor EP4 subtype in rat adrenal zona glomerulosa: Involvement in aldosterone release

We examined the role of prostaglandin (PG) E receptors in the secretion of aldosterone. PGE(2) is known to exert its various biological functions by b inding to PCE receptors. There are four subtypes of PGE receptors, EP1, EP2 , EP3, and EP4. Among the PGE receptors EP1 and EP4 subtypes a:re coupled t o Gs protein and stimulate adenylyl cyclase. In this study, PGE(2) caused a dose-dependent increase in aldosterone production from the rat adrenal zon a glomerulosa cells in vitro accompanied with an increase in intracellular cAMP concentration. A specific agonist for EP2, butaprost, did not increase the cAMP production or the aldosterone release, suggesting the possibility that EP4 mediates the secretion of aldosterone by PGE(2). Northern blot hy bridization analysis disclosed that EP4 gene was expressed in the rat adren al gland but that EP2 gene was not. In situ hybridization revealed that EP4 mRNA is present abundantly in the zona glomerulosa of rat adrenal gland. T hese findings suggest that the PGE(2)-EP4 system is involved in the regulat ion of aldosterone secretion from the rat adrenal gland.