Purification, Partial Characterization and Metabolism of an Acid Labile Conjugate of Aldosterone12

Abstract

An acid labile conjugate of aldosterone was extracted from the urine of a normal subject following the oral administration of a mixture of d-aldosterone and 7-³H-aldosterone. Tests on the purified conjugate for sulfate and phosphate were negative, but a positive reaction with napthoresorcinol reagent was obtained, suggesting, together with other evidence, that the conjugate is a glucuronide although it is not readily hydrolyzed by bacterial or mammalian liver β-glucuronidase. The radioactive steroid moiety released from the conjugate by pH 1.0 hydrolysis was shown to be aldosterone. The metabolism of the purified tritiated conjugate was studied by examining the pattern of radioactivity excreted in the urine following intravenous injection of the conjugate into 3 normal humans. About 81 % of the injected radioactivity was excreted in the urine as unchanged conjugate in the first 6 hr. In one experiment, ¹⁴C-aldosterone and tritiated conjugate were injected simultaneously and the ¹⁴C/³H ratio of the conjugate in the urine gave a measure of the production rate of the conjugate. The 4 metabolism experiments indicate that about 23% of the secretion of aldosterone is converted to the conjugate in normal subjects.