INTERACTION BETWEEN HYDROCORTISONE-4-C14OR PROGESTERONE-4-C14AND SERUM ALBUMIN AS DEMONSTRATED BY ULTRACENTRIFUGATION AND ELECTROPHORESIS

Abstract

SOLUBILITY studies in aqueous systems have demonstrated considerable interaction between various steroid hormones and serum albumin. Human plasma dissolved about 2.5 times as much hydrocortisone as water; a five-fold increase of the water-solubility was observed in a 25% human serum albumin solution (Macek et al, 1952). Approximately 20 or 30 times the amount of progesterone, soluble in water, could be dissolved in 6% albumin or in serum, respectively (Bischoff et al., 1954). The interactions with serum albumin and possibly other serum proteins result in maximal binding capacities of serum for these steroid hormones corresponding to about 1,000 to 10,000 times their physiological concentrations. The present studies tend to clarify the status of interaction between hydrocortisone or progesterone and serum albumin at concentrations close to physiological. Such knowledge is considered essential for an understanding of the transport mechanism of the steroid hormones which in turn is believed to be related to their mode of action.