Rat Ovarian 20α-Hydroxy steroid Dehydrogenase: Effects of Estrogens and Pituitary Gonadotrophins1

Abstract

High levels of rat ovarian 20ahydroxysteroid dehydrogenase activity relate to the presence of mature or freshly ruptured follicles, while low values are associated with a “functioning” corpus luteum. Secretion of 20α-hydroxypregn-4-en-3-one from the rat ovary coincides with the level of steroid dehydrogenase activity in the gland. Estrogen administration failed to increase or induce 20α- hydroxysteroid dehydrogenase activity in pseudopregnant or prepubertal rats, negating a direct stimulatory action of estrogen on the enzyme or on the synthesis of new enzyme protein. Follicle-stimulating hormone and luteinizing hormone failed to initiate steroid dehydrogenase activity or to cause ovulation in prepubertal rat ovaries when administered alone or with diethylstilbestrol. Simultaneous administration of luteinizing hormone and follicle-stimulating hormone, on the other hand, produced measurable enzyme activity and resulted in ovulation, estrogen secretion and corpus luteum formation.