Endocrinology, Vol 110, 1749-1757, Copyright © 1982 by Endocrine Society

ARTICLES

delta 4-Hydrogenase in guinea pig adrenal: evidence of localization in zona reticularis and age-related change

KO Martin and VH Black

The guinea pig adrenal increases in the size with age, yet cortisol secretion per gram adrenal declines. It has been suggested that this could be due to catabolism of cortisol by increased adrenal delta 4- hydrogenase. In this paper we show that delta 4-hydrogenase is localized in the zona reticularis and increases coincidently with the large increase in the volume of this zone with age. Glands were microdissected to give inner vs. outer cortices, and the postmitochondrial supernatants of these two portions were assayed for delta 4-hydrogenase activity. The enzyme was found almost solely in preparations from inner cortices, which were predominantly zona reticularis. Cells were isolated from each portion and assayed for delta 4-hydrogenase activity. Again, only those which contained zona reticularis cells, that is, those from the inner cortices, had activity. The activity was shown to be present in both microsomes and cytosol, although the latter was preferentially expressed in a 15,000 X g supernatant. When the metabolites were separated by thin layer chromatography, the products of the microsomal enzyme were 5 alpha- and 5 beta-dihydrocortisol (1:1) and that of the cytosolic enzyme was 5 beta-dihydrocortisol, whereas in the 15,000 X g supernatant the 5 beta- isomer was the predominant product. Its identity as 5 beta- dihydrocortisol was confirmed by mass spectroscopy. Tetrahydrocortisol comprised a minor portion of the products.