DETERMINATION OF 3$-HYDROXYSTEROID DEHYDROGENASE SYSTEM IN MICROGRAM SA1\IPLES OF TISSUE, QUANTITATIVE HISTOLOGIC DISTRIBUTION OF THE ENZYME IN THE RAT ADRENAL AND EFFECTS OF ADRENOCORTICOTROPIN’

A fluorometnic method for determination of the 3fl-hydroxysteroid dehydrogenase systens its microgram samples of tissue, based on nicotinamide adenine dinucleotide redirctiotm by pregnermo-lone, was developed and applied to the quantitative histologic distributions of time emszynse in the adrenal gland of the rat. Single subcutaneous injections of adrenocorticotropin iii saline solution (25 mg/kg) and daily injections for 6 days of the same dose in gel resurlted in nmo demon-strable influence on either the activity or distribution of the enzyme. The distriburtiomm observed was relatively urniform throughout the cortex, although a tendemicy to greater activity its the glomerulosa was found in some cases, and no appreciable activity was seen in the medulla. The data supported those in the literature, indicating that this enzyme is not rate limitimug in the biosynthesis of corticosterone in the adrenal following stimulation by adremmocorticotropin. 3j3-Hydroxysteroid: NAD oxidoreductase (also called 3-hydroxysteroid dehydrogenase) has been defined (9) as the enzyme that catalyzes the reaction of 3f-hydroxysteroids with nicotin-amide adenine dinucleotide to yield ketosteroid