URINARY PORTER-SILBER CHROMOGEN VERSUS BLUE TETRAZOLIUM CHROMOGEN AS A QUANTITATIVE INDEX OF ADRENOCORTICAL FUNCTION

Abstract

METHODS thus far published for the estimation of urinary metabolites of the adrenocortical steroids have given only partially satisfactory estimates of adrenocortical function. The most widely used chemical procedure for the measurement of urinary corticosteroids has been the phenylhydrazine-sulfuric acid reaction as introduced by Porter and Silber (1). This reaction is specific for the determination of those cortical steroids which contain both an alpha ketol grouping and a hydroxyl group at the C₁₇ position (1–3). Since some of the alpha ketolic corticosteroids elaborated by the human adrenal gland, such as aldosterone and corticosterone (4, 5), do not possess a 17-hydroxyl group, the Porter-Silber reaction cannot be used to measure this class of adrenocortical steroids. A method for the measurement of alpha ketolic corticosteroids based on the reduction of blue tetrazolium [3,3′-dianisole-bis-4,4′-(3,4-diphenyl)-tetrazolium chloride] in alkaline media was developed by Mader and Buck (6). This reaction does not depend upon the presence of a 17-hydroxyl group and therefore can be used to determine both those steroids which react with the Porter-Silber reagent and those which contain only an alpha ketol grouping at the C₁₇ position. Chen and associates have reported that Δ⁴-3-keto and 17-α-hydroxy-20-keto groups also exhibit reducing power for blue tetrazolium; but calculated on a molar basis, their power of reduction is only from 5 to 10 per cent of that of alpha ketolic steroids (7). The blue tetrazolium method has been modified for application to urinary extracts by Chen et al. (7, 8) and more recently by Sulkowitch and co-workers (9).