Characterization of ovarian folliculogenesis during the luteal phase of the menstrual cycle in rhesus monkeys using [3H]thymidine autoradiography.

The characteristics of the early stages of ovarian follicular maturation were investigated in rhesus monkeys during the luteal phase of the menstrual cycle using a novel procedure to supply low levels (10 microCi) of [3H]thymidine directly to ovaries in vivo. With this labeling procedure, plasma levels of [3H]thymidine did not exceed 8 cpm/microliters and labeled ovarian cells were readily identifiable by autoradiography. Results from four animals studied during the luteal phase of the cycle indicated that all sizes of preantral follicles contained granulosa cells that incorporated [3H]thymidine. There was a progressive increase in the percentage of labeled follicles in direct relationship to follicular size; 10% of the single granulosa cell layer follicles were labeled and the labeling frequency increased to greater than 60% in the large (> 6 granulosa cell layer) preantral follicles. The labeling frequency of all size classifications of preantral follicles during the luteal phase of the menstrual cycle was similar to that of an animal which was studied during the follicular phase of the menstrual cycle. The results suggest that growth of ovarian follicles to the preantral stage occurs during the luteal phase of the menstrual cycle in rhesus monkeys, and thus the cessation of preovulatory folliculogenesis during the luteal phase of the cycle is not due to a defect of growing preantral follicles.