In VitroandIn VivoOvarian Steroidogenesis in the Long Term Hypophysectomized Hamster*

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Abstract
Hamsters hypophysectomized between 1200–1300 h on day 4 (proestrus) did not ovulate the next morning (day 1). All antral follicles became atretic within 6 days, and ovarian development was limited to small- and medium-sized preantral follicles and interstitial cells. Serum levels of progesterone (P) were consistently less than 1 ng/ml from days 1–20. Serum 17β-estradiol (E2) and testosterone (T) also decreased concurrently but remained at relatively high levels until day 2. Thereafter, serum T levels remained the same and E2 levels were below the sensitivity of the assay (≪6 pg/ml) through day 20. The ovarian concentrations of P, E2, and T were low from days 1–20. The steroidogenic capacity of the ovary at different times after hypophysectomy was assessed by 2-h in vitro incubation in Krebs-Ringer bicarbonate. One to 8 days after hypophysectomy, the ovary in vitro produced large amounts of P (5–7 ng/mg·h); thereafter, P decreased significantly, but the ovary still synthesized appreciable amounts of P through day 20 (1 ng/mg-h). The ovary in vitro produced about 2 pg/mg·h T on days 1–20 and about 2 pg/mg-h E2 from days 1–10. A single ip injection of 5 jug LH on either day 6 or 20 resulted in significant increases in the concentrations of ovarian P and T and in vitro production rates of P and T 3 h later. Serum P was significantly elevated over saline control values 2–21 h after injection on day 6 or 20; however, there was no effect of LH on serum levels of T and E2. The increase in serum P did not occur in hypophysectomized ovariectomized hamsters treated with LH, indicating that the adrenal was not involved in the response. Thus, steroidogenic activity is demonstrable in vitro for hamster ovaries deprived of gonadotropin support for 3 weeks, and exogeneous LH stimulates rapid synthesis and secretion of P and T. (Endocrinology106: 1093, 1980)