In vitro evidence of steroidogenesis in the amphibian (Rana pipiens) ovarian follicle and its relationship to meiotic maturation and ovulation
✍ Scribed by Snyder, Ben W. ;Schuetz, A. W.
- Publisher
- John Wiley and Sons
- Year
- 1973
- Tongue
- English
- Weight
- 692 KB
- Volume
- 183
- Category
- Article
- ISSN
- 0022-104X
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✦ Synopsis
Abstract
Cyanoketone (CK) was used to investigate the involvement of steroidogenesis on gonadotropic hormone‐induced oocyte germinal vesicle breakdown and ovulation in frog ovarian follicles in vitro. Cyanoketone inhibited pituitary hormone‐induced oocyte meiotic maturation and ovulation but had no inhibitory effects on progesterone‐induced germinal vesicle breakdown. In contrast, CK inhibited meiotic maturation induced by low but not high doses of pregnenolone. The effect of CK on the uptake and metabolic conversion of ^3^H‐pregnenolone by ovarian follicles was also studied. Ovarian follicles removed ^3^H‐pregnenolone from the incubation medium and frog pituitary homogenate stimulated the net uptake of this steroid by nearly 60%. Cyanoketone had no effect on this uptake. Thin layer chromatographic analysis of extracts of ovarian follicles previously incubated in ^3^H‐pregnenolone, indicated that radioactive progesterone as well as other products were synthesized in the presence or absence of pituitary hormones. Cyanoketone inhibited the amount of ^3^H‐pregnenolone converted by the follicles and similarly reduced the formation of steroid corresponding chromato‐graphically to ^3^H‐progesterone. These results indicate that metabolism of pregnenolone occurs in the amphibian follicle and that CK interferes with this process presumably as a result of the inhibition of 3β‐hydroxysteroid dehydro‐genase. These data further suggest that this enzyme is an important link in gonadotropic initiation of meiotic maturation and ovulation in amphibian ovarian follicles.