The proposed research is intended to characterize further the catecholamine synthesizing enzyme dopamine-beta-hydroxylase (DBH) as it pertains to humans. These goals will be accomplished by (1) isolating the enzyme from human tissues (i.e.pheochromocytoma, plasma, adrenal glands). (2) comparing the molecular properties with those of the better studied bovine DBH. (3) developing a radioimmunoassay for human DBH in order to help define the relationship of plasma DBH and sympathetic nervous system activity. Human DBH will be isolated from pheochromocytoma via ion-exchange and gel filtration chromatography. An affinity chromatography technique will be developed for purification from plasma and adrenal gland. The enzyme will be characterized regarding molecular weight, subunit size and structure, copper content, amino acid and carbohydrate composition, and specific activity. The human enzyme will be further characterized regarding the in situ distribution of its particulate and soluble forms. In addition, the relationship of soluble DBH to catecholamine release will be defined via isolation and lysis of intact chromaffin vesicles. A radioimmunoassay (RIA) will be developed for the human enzyme, which appears to be immunologically quite different from bovine DBH. Plasma DBH will be determined both by RIA and enzymatic assay in normal subjects and subjects with various forms of hypertension. Immunologic and enzymatic activity of plasma DBH will be correlated with urinary catecholamines and catecholamine metabolites before and after acute stresses (in normal subjects and subjects with hypertension).