A radioimmunoassay for the measurement of tetrahydroaldosterone 3-glucosiduronic acid in human plasma.

A simple, reliable and specific radioimmunoassay procedure for the measurement of the principal aldosterone metabolite, tetrahydroaldosterone 3-glucosiduronic acid, in human plasma is described. The glucosiduronate is extracted from plasma (generally 200 microliter) by the use of Amberlite XAD-2 resin, eluted with acidic, aqueous ethanol, separated from unconjugated steroids by partition and estimated using a specific antibody. A disequilibrium system is used, but with a conventional charcoal separation; the advantages of such a system are discussed. Data obtained by incorporating chromatographic separations into the assay procedure is presented as evidence for the specificity of the method. Data concerning the long-term storage of plasma samples is given, together with plasma concentrations of the glucosiduronate in both normal people and in people with abnormalities of aldosterone secretion.