Renin-angiotensin system, adrenal steroids and sodium depletion in a primitive mammal, the American opossum.

Abstract

Intravenous infusion of a mammalian ACTH or an opossum renin preparation into opossums given dexamethasone to suppress anterior pituitary function resulted in significant increases in the secretion rates of cortisol, corticosterone and aldosterone. Steroid measurements were made by the double isotope derivative assay method. Stimulation of adrenal steroidogenesis by a renin preparation was also demonstrated in the hypophysectomized opossum. The major steroid secreted by the adrenal gland of the opossum was cortisol, but substantial amounts of aldosterone and corticosterone were present in adrenal vein plasma. The opossum renin preparation produced a slow, prolonged pressor response and, similar to other mammalian renin preparations, was heat labile, stable at pH 2.6 and nondialyzable. Sodium depletion in the opossum was associated with a significant increase in the juxtaglomerular index of granulation in the kidneys. The data are consistent with the existence of a functional reninangiotensin- aldosterone ...