[Changes in ovarian 3 beta-hydroxysteroid dehydrogenase and 20 alpha-hydroxysteroid dehydrogenase activities in...

Changes in ovarian 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) and 20 alpha-HSD activities were studied in pregnant rats. The activity of 3 beta-HSD was determined by measuring the rate of conversion of pregnenolone to progesterone. The activity of 20 alpha-HSD was determined by measuring the rate of conversion of 20 alpha-hydroxy-pregn-4-en-3-one to progesterone. 3 beta-HSD activity in corpora lutea (CL) was low between days 8 and 12, increased rapidly on day 15, and then gradually decreased until day 23. 20 alpha-HSD activity in CL markedly decreased from days 8 to 18, and then increased until day 23. The activities of 3 beta-HSD and 20 alpha-HSD in non-luteal ovarian compartment (NLO) showed no significant changes between days 8 and 23. These results indicated the important role of these enzymes in the secretion of progesterone from CL. It was also suggested that these enzyme activities in NLO might be controlled by a different mechanism.