INFLUENCE OF MAMMALIAN AND AVIAN GONADOTROPINS ON INVITRO OVARIAN STEROID SYNTHESIS IN TURTLE (CHRYSEMYS-PICTA)

The synthesis of steroids from 7.alpha.[3H]cholesterol and 7.alpha.[3H]pregnenolone by turtle ovarian tissues in vitro was studied. Pregnenolone, 17.alpha.-hydroxypregnenolone, progesterone, 17.alpha.-hydroxyprogesterone, androstenedione, testosterone, dehydroepiandrosterone, estrone, estradiol 17.beta., estriol and 16-epiestriol were identified as products. All estrogens were detectable in incubates of preovulatory follicular tissue, but only small quantities of estrone were found in incubates of follicular tissue from postovulatory animals and luteal tissue. The effects of mammalian and avian gonadotropins on the metabolism of tritiated precursors were studied. Both mammalian (ovine) and avian (chicken) luteinizing hormone (LH) were stimulatory when conversion of cholesterol or pregnenolone to major steroid products was examined. Enhancement of estrogen biosynthesis predominated in preovulatory follicular tissue, whereas increased progestin yield was the major effect in follicular and luteal tissue from postovulatory animals. The effects of ovine FSH (follicle stimulating hormone) were minimal compared to the same dose of LH. A slight increase in estrogen yield was only noted when preovulatory follicular tissue was incubated with cholesterol and mammalian FSH, and neither mammalian nor avian FSH had an effect on pregnenolone conversion by follicles from postovulatory animals. Prolactin (bovine) had no effect on luteal progesterone synthesis when used alone, but reduced the stimulatory effect of mammalian LH on progesterone synthesis. 11-Deoxycorticosterone was not a product of the turtle ovary under normal conditions or after in vitro ACTH stimulation.