Abstract
A method is described for assaying aldosterone-stimulating activity in vitro using adrenal glands of rats kept on a sodium deficient diet. The production of aldosterone and corticosterone was measured by double isotope dilution derivative assays. Addition of ACTH or precursor steroids and elevation of the potassium concentration in the incubation medium gave a significant increase of aldosterone production. Angiotensin II showed little aldosterone-stimulating activity and only at a very high concentration. Small doses of a purified extract from human urine lead to a reproducible, significant and dose-dependent increase of aldosterone production without influencing production of corticosterone. The theoretical and practical advantages and limitations of the method are evaluated.