Stimulation of Various 17β and 20α-Hydroxysteroid Dehydrogenase Activities by Progestins in Human Endometrium*

Abstract

The activities of 17β and 20α-hydroxysteroid dehydrogenases in homogenates of human endometrium were measured using estradiol, testosterone, 5-androstene-3β,17β-diol, and 20α-dihydroprogesterone (20α-DHP) as substrates. All of these activities were about 20 times higher in secretory tissue than in proliferative endometrium. The rates of oxidation of the three 17β-hydroxysteroids tested were similar and about 4–8 times higher than the rate of oxidation of 20α-DHP under the same assay conditions. Fragments of proliferative endometrium were incubated under organ culture conditions for 1–3 days in either medium alone or medium to which various amounts of progesterone or medroxyprogesterone acetate were added. As reported before, 3 to 10-fold increases in 17β-hydroxysteroid dehydrogenase activity, determined by measuring the rate of conversion of estradiol to estrone, were noted during incubations in the presence of progestins. Similar increases were observed when testosterone, 5-androstene-3β,17β-diol, and 20α-DHP were used as substrates in the enzymatic assay. The parallelism in response of these activities to progestin stimulation in vitro was also evident when time of incubation and concentration or type of progestins were varied. These results show that progestins enhance the activity of dehydrogenases involved in the metabolism of estrogens, androgens, and progestins in human endometrium and provide evidence suggesting that these activities reside in a single dehydrogenase.