The reversible oxidation of 3α-hydroxysteroids to their corresponding 3-keto forms comprises an important step in the metabolism of C19-steroids. The described techniquue demonstrates the activity of the enzyme catalyzing this reaction, with the use of androsterone as a substrate and a tetrazolium salt as the final electron acceptor. The enzyme is specific for 3α-hydroxysteroids; there was no histochemical reaction with epiandrosterone, the β isomer of androsterone. Since 3α-hydroxysteroid dehydrogenase is soluble in aqueous solutions, it was necessary to increase the osmolarity of the incubation medium by adding polyvinylpyrrolidone in a final concentration of 20%. Although the enzyme has a dual nucleotide specificity, no appreciable differences were seen in its distribution pattern in rat tissues with either NAD or NADP as a coenzyme. In adult female rats, enzyme activity was present in the liver, kidneys and clitoral glands. In mature males, diformazan deposits were observed in the liver, kidneys, preputiai glands, epididymis, ventral prostate and Leydig cells.
The Nucleotide Specificity and Feedback Control of Thymidine Diphosphate d-Glucose Pyrophosphorylase
