The proposed research is designed to elucidate the relationship of renal medullary prostaglandins to the vasopressin prostaglandin system of the renal medulla, and to the development of experimental hypertension. The experimental models involve in vitro and in vivo procedures. The in vitro procedures will be designed to study the effect of hyperosmolality on the ultrastructure of the the interstitial cells and the synthesis, release and inactivation of PG by tissue slices. The in vivo model to be studied in the same manner will be experimental unilateral hydronephrosis drug obstruction and drug relief of obstruction. Experimental hypertension of the renal artery constriction type with contralateral hydronephrosis will be studied.