The proposed research program will focus on properties of the cellular components of blood vessels, endothelium and smooth muscle, which influence their reactivity to vasoactive mediators. Using established, as well as newly developed methods, blood vessel cells (human, bovine, rodent) will be isolate and cultured for biochemical and physiological studies. Angiotensin II receptors will be characterized by radioligand binding assays, and the regulation and biochemical consequences of their activation studied, including interrelations with prostaglandin and cyclic nucleotide metabolism. Factors influencing endothelial cell angiotensin-I converting enzyme activity also will be studied. The above studies will be extended to vascular preparations obtained from spontaneously hypertensive rats and rats with experimentally-induced alterations in renin-angiotensin system activity.