16a-Hydroxysteroids

R4. Reynolds, J. W., The excretion of two A -3/3-OH,16a-hydroxysteroids by patients with congenital adrenal hyperplasia. Pediatrics 36, 583-591 (1965). 

Acoxy compounds from ethers—16a-Hydroxysteroids s. 11, 23 I Competitive 0-debenzylation... 

Mechanism of action Prednisone itself is inactive and must first be reduced to prednisolone by 11-p-hydroxysteroid dehydrogenase7. The steroid binds to a receptor that triggers the production of specific proteins (see Figure 38.16A). The specific mechanism for its lymphocytopenic action after interaction with DNA remains to be elucidated. 

Metabolism studies. GC-MS is a powerful technique for following and identifying the metabolic products from the in vitro incubation of tissue preparations with steroid substrates. Examples of such studies include the 16a-hydroxylation of 18-hydroxydeoxycorticosterone by human adrenal gland [254], the eiromatization of 3jS,15, 16 -trihydroxy-5-androsten-17-one by placental homogenates [255], and the demonstration of 1/3, 12/3, 6a and 6/3 hydroxylase enzyme activities in microsomal preparations of human foetal hepatic tissue [256]. In the latter study, testosterone was used as substrate and in addition to the hydroxylated metabolites isolated, several other testosterone derivatives indicated the presence of 3a, 3/3 and 17/3-hydroxysteroid oxidoreductase in the adrenal gland preparation. 

After the first demonstration of a direct metabolism of a steroid conjugate [androstenediol sulfate =i dehydroepiandrosterone sulfate (Baulieu et ah, 1963)], showing that a 17j8-hydroxysteroid oxidoreductase can have a sulfo conjugate as a substrate, other enzymic transformations of dehydroepiandrosterone sulfate were reported (Fig. 4). Dehydroepiandrosterone sulfate can undergo 16o -hydroxylation to 16a-hydroxy-dehydroepiandrosterone sulfate which can be further hydroxylated into androstenetriol sulfate its direct 17-hydroxylated metabolite, androstene-... 

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