Effect of luteinizing hormone and cyclic adenosine 3',5'-monophosphate on steroidogenesis in the ovarian follicle of the rabbit

Abstract

Mature ovarian follicles have been isolated from estrus rabbits and the effects of gonadotropin and cyclic AMP on steroidogenesis in this tissue determined. Gonadotropins used include LH, FSH, and prolactin; follicular levels of progesterone, 17-hydroxyprogesterone, testosterone and 17beta-estradiol in all experiments were quantitated by radioimmunoassay. Incubation of follicles with LH in concentrations ranging from 0.05 to 50 mug/ml medium yielded increases in the total ng steroid/follicle. Five mug LH/ml gave a maximal response with no further increase in steroid concentration when the LH was raised to 50 mug/ml. Prolactin had no effect on follicular steroidogenesis while the stimulatory action of a FSH preparation could only be partially attributed to LH contamination. Cyclic AMP also proved to be a potent stimulatory agent in follicular steroidogenesis with maximal increases at 20 mumoles/ml and a decline in the ng steroid/follicle when cyclic AMP was raised to 30 and 40 mumoles/ml. The effects of LH and cyclic AMP proved to be nonadditive; incubation of follicles simultaneously with 5 mug LH/ml and 20 mumoles cyclic AMP/ml yielded steroid concentrations which were no different than levels following incubation with either agent alone. Taken together, these results demonstrate that both LH and cyclic AMP cause increases in radioimmunoassayable steroid in the rabbit follicle in vitro and that LH probably acts by way of a cyclic AMP intermediate.