The renin-angiotensin-aldosterone system and the prostaglandins (PG's) play important roles in the maintenance of blood pressure and salt and water balance. The proposed studies will investigate the interactions between angiotens in II (AII) and metabolites of arachidonic acid in the regulation of aldosterone secretion by adrenal zona glomerulosa cells. Previous studies suggested that PG's are involved in the stimulation of aldosterone synthesis by AII since PG synthesis inhibitors reduce AII-induced steroidogenesis. The adrenal metabolized arachidonic acid to PG's, hydroxy-eicosatetraenoic acids (HETE's), diHETE's and epoxides (EET's); however, AII stimulates only the release of a non-polar PG of unidentified structure, 6-keto-PGF1Alpha, and non-polar metabolites migrating with the HETE's. The hypothesis will be tested that AII stimulates the synthesis of a PG(s), HETE(s), diHETE(s), EET(s) or leukotriene (LT)(s) in the adrenal and the released eicosanoid(s) modifies the steroidogenic action of the peptide. The adrenal metabolites of arachidonic acid will be isolated and identified by HPLC, synthesized, and tested for their ability to alter basal and AII-stimulated steroidogenesis. Assays will be developed for those metabolites that are biologically active in physiologically relevant concentrations. The relationship between aldosterone and metabolite release will be determined in cells stimulated by AII to find out if the peptide stimulates the synthesis of the metabolite and if the concentrations of the metabolite are adequate to alter steroidogenesis. These studies will be repeated in the presence of inhibitors of the arachidonic acid metabolizing pathways. Further studies into the biosynthesis, site of action and mechanism of action of the metabolite(s) will also be performed. The adrenal also contains the fatty acid adrenic acid (C22:4) that was found to stimulate aldosterone secretion. The metabolism of adrenic acid will be investigated in a similar manner, and the role of 22 carbon PG's, hete's etc., in its steroidogenic action determined.
