Steroid-Protein Interactions: IX. Interaction of Aldosterone with Human Serum Proteins in Competition with Spirolactones and Other Steroids

Abstract

The effect of spirolactones (SC-9420 and SC-8109) on aldosterone binding to serum proteins was studied and compared with the competitive effect of other steroids, in order to investigate the possibility that the antagonism of aldosterone by spirolactones may be mediated through a competition for protein binding sites. Aldosterone was found to interact more strongly with whole human serum than with albumin, at both 37 and 4 C. Relatively large concentrations of spirolactones were required to displace aldosterone from human serum proteins; similar displacement was obtained with small concentrations of cortisol or progesterone. Variations in the serum levels of endogenous 17- hydroxycorticosteroids, produced by suppression of adrenocortical secretion or by ACTH administration, were shown to affect aldosterone binding.