The Identification of the Porter-Silber Chromogen Secreted by the Rat Adrenal*

The rat adrenal gland secretes a Porter-Silber chromogen with a mobility of 0.6 relative to corticosterone in toluene-propylene glycol (l-3) .I It does not reduce tetrazolium derivatives and differs in this respect from steroids containing a dihydroxyacetone side chain, which reduce tetraeolium, and from the 20keto-21 aldehydes which do not reduce tetrazolium but react more rapidly with the Porter-Silber reagent than do ketols with a hydroxyl group at C17 (4-7). The secretion of this compound is greatly increased by adrenocorticotropic hormone (2). The material is inactive in the eosinopenia assay but appears to have sodium-retaining activity comparable to that of deoxycorticosterone (7). Previous studies have indicated that the substance is a steroid with a A4-3-ketone function but no ketone group at Cl1 and C17, that it lacks hydroxyl groups at Cg and at Crr, and that it forms two acetylated derivatives (7). These conclusions were based on absorption spectra, obtained in methanol and in sulfuric acid, and upon treatment with dinitrophenylhydrazine and diphenylamine, on the Zimmermann test before and after oxidation with various oxidizing agents, on various spot tests, and on the properties of the products obtained after acetylation. This paper presents evidence strongly suggesting that the unknown compound is the 20 ---f 18 cyclic hemiketal of 1% hydroxy-11-deoxycorticosterone.