Localization, purification, and biological activity of a new aldosterone-stimulating factor.

An aldosterone-stimulating factor (ASF) has been isolated from normal human urine and found to be a glycoprotein with a molecular weight of 26,000 daltons. ASF stimulated aldosterone production both in vivo and in vitro. ASF was found to be different from other known aldosterone secretogogues by the use of high performance liquid chromatography (HPLC). The retention time of ASF was different (17.0 minutes) from ACTH (retention time, 28.4 minutes), beta-lipotropin (retention time, 20.5 minutes), and angiotensin II. Proteolytic enzyme digestion and purification of ASF by HPLC yielded a smaller molecule (retention time, 22.0 minutes) with a molecular weight of 4000 daltons. This smaller molecule also stimulated aldosterone production in vitro. This showed that the structural requirement for steroidogenesis may be residing in a smaller molecule. ASF failed to produce hypertension in adrenalectomized rats. By immunofluorescence (using fluorescein conjugated antibodies), ASF was found to be localized in the anterior lobe of the pituitary gland. Data suggest that ASF, a new aldosterone-stimulating hormone that has not been described before, is secreted by the pituitary gland, and the adrenal gland appears to be the target organ for the biological activities.