The roles of prolactin and testosterone in the development and function of granulosa lutein tissue in the rat

The luteotropic roles of prolactin and testosterone (or estradiol formed in luteal tissue) were investigated in hypophysectomized rats with homografts of granulosa lutein tissue. Using this approach, we could determine the effects of prolactin independently of estrogen, since granulosa lutein tissue does not produce estrogen de novo under these conditions. Luteinizing granulosa cells were expressed from the ovaries of immature pregnant mare's serum gonadotropin-primed Fischer 344 rats 6 h after injection of human chorionic gonadotropin. The cells were transplanted beneath the kidney capsule of adult, hypophysectomized, ovariectomized Fischer 344 recipients, which were treated with hormones daily for 12 or 14 days. In rats without treatment (no hormones, n = 3) and in rats treated with only testosterone (Silastic capsule, n = 6), only small amounts of luteal tissue (less than 5 mg/rat) were found and serum progesterone remained at low concentrations (10 ng or less) throughout the experiment. In contrast, in rats treated either with ovine prolactin (300 micrograms/day, n = 10) or with the combination of prolactin and testosterone (n = 12), serum progesterone increased to 43 ng/ml by Day 8. Beyond Day 8, serum progesterone continued to rise in rats treated with the combination of prolactin and testosterone to reach a mean value of 87 ng/ml by Day 14, and mean homograft wet weight was 49 mg/rat; in rats treated with only prolactin, serum progesterone decreased to 25 ng/ml by Day 14 and homograft wet weight was lower (24 mg/rat). Prolactin and testosterone together stimulated more homograft aromatase activity in vivo than did prolactin alone, but the in vitro production of progesterone was not different.(ABSTRACT TRUNCATED AT 250 WORDS)