THE IN VITRO BIOSYNTHESIS OF 18-HYDROXYCORTICOSTERONE-4-14C BY SLICES OF ZONA GLOMERULOSA OF BEEF ADRENALS AND BY HUMAN ADRENALS

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Abstract
The in vitro steroidogenesis of the zona glomerulosa of beef adrenals and that of human adrenals was investigated. Tissue slices were incubated in a Krebs-Ringer - bicarbonate medium containing 200 mg% of glucose with progesterone-4-C14 and corticosterone-4-Cl4 as precursors. After incubation-the media were extracted exhaustively with chloroform and the dry residue of the solvent extract fractionated on paper chromatographic systems. The identity of one of the C14 transformation products produced from both precursors was investigated in detail. The substance absorbed ultraviolet light ([lambda] EtOH. 241 m/[mu]), max'' but reduced alkaline blue tetrazolium only very slowly. The mobility of the unknown alone and diluted with inactive carrier was identical with that of the 20[forward arrow] 18 cyclic hemiketal of I8-hydroxycorticosterone. The identity of the biosynthetic material with the closed form of 18-hydroxycorticosterone was established by isotopic dilution techniques and the formation of derivatives. It was observed that the compound can exist in at least three different tautomeric forms. The yield of 18-hydroxycorticosterone with beef zona glomerulosa was 3.8% from progesterone and 6.8% from corticosterone. Human adrenal slices transformed progesterone to 18-hydroxycorticosterone in a yield of 0.5%, while the transformation from corticosterone was around 1%. Incubation of biosynthetic 18-hydroxycorticosterone-4-C14 with beef zona glomerulosa slices yielded small amounts of aldosterone and a sub-stance probably identical with the 11-dehydro-derivative of the pre-cursor. Aldosterone-4-C14 incubated with the same tissue was not transformed to 18-hydroxycorticosterone. It is concluded, that although 18-hydroxycorticosterone is produced in relatively large quantities in both bovine and human adrenals, it is not an immediate precursor of aldosterone.