Gonadotropin-stimulated uptake of steroid hormones by Rana pipiens ovarian follicles incubated in vitro

The uptake of [ 3H]pregnenolone by frog ovarian follicles incubated in vitro is stimulated 50–60% by frog pituitary homogenate. This effect is mimicked by mammalian LH, but not by other pituitary or placental hormones. The uptake of progesterone is also stimulated by pituitary hormone, whereas, 17β-estradiol uptake is not. Incubation of follicles for less than an hour with gonadotropic hormones is sufficient to stimulate steroid uptake, and this process is fully inhibited by puromycin and partially inhibited by actinomycin D. Removal of follicular envelope interferes with the action of the pituitary hormone. Increasing concentrations of steroid hormone (pregnenolone) in the incubation medium stimulated [ 3H]pregnenolone uptake to an even greater extent than pituitary hormones. The possibility that gonadotropin-stimulated uptake of progestins is mediated by synthesis of a pregnenolone-like steroid is discussed.