Follicles were isolated from rabbits before and after mating and the effects of LH on steroidogenesis were studied using an incubation technique. Before mating testosterone was the major steroid produced in response to LH. Mating or administration of ovine LH
in vivocaused the follicles to produce mainly progesterone and these follicles were refractory to LH in vitro. Up to 72 h after mating, LH would stimulate follicles to produce progesterone. At 96 h after mating, the testosterone response to LH was again manifest. These results suggest that the responsiveness of rabbit follicles to LH is dependent on the endocrine status of the animal when the ovaries were removed.