Estradiol and 20alpha-dihydroprogesterone dehydrogenase activities in human endometrium during the menstrual cycle.

Abstract

Estradiol dehydrogenase E2-DH)and 20α-dihydroprogesterone dehydrogenase (20αDHP-DH) activities in human endometrium at various phases of the menstrual cycle were measured by incubating 3H-estradiol or 3H-20α-dihydroprogesterone (20αDHP) with an 800 × g supernatant of tissue and excess NAD*. The enzymatic activities, expressed as nmoles of product formed per hr and per mg of protein, showed a significant increase during the secretory phase. The average values of E2-DH activities were 1.2 in proliferative endometrium and 14 in secretory tissue. The corresponding 20αDHP-DH activities were lower (0.3 and 3.0). The total amount of E2 receptors in endometrium, determined by the method of superfusion, was found o t decline from 3.2 pmole/mg DNA in the proliferative phase to 0.6 pmole/mg DNA at the end of the secretory phase. The increase in E2-DH levels leads to a faster removal of E2 from endometrium since the conversion of E2 to E2 is only partially reversible and E1 rather than E2 is released by the tissue. T...