The Effects of Phenobarbital and Gonadal Steroids on Periovulatory Serum Levels of Luteinizing Hormone and Follicle-Stimulating Hormone in the Hamster

Abstract

The occurrence of ovulation and serum levels of LH and FSH (measured by radioimmunoassay) were determined in periovulatory hamsters injected with an ovulation-blocking dose of phenobarbital (Phen) combined with progesterone (P), estradiol-17beta (E2), or testosterone (T). Proestrous hamsters were treated at 1300 h with Phen plus oil, P, P plus E2, E2, T, or a second injection of Phen at 2000 h. Each treatment group was divided into 3 subgroups, each of which was serially bled 4 times at 6 h intervals beginning at 1200, 1400, and 1600 h on proestrus. Phen blocked ovulation on the next morning in all animals, while treatments that included P (1 mg) restored the normal complement of ova in 65-75% of the animals. Neither E2 (1, 10 or 50 mug) nor T (0.1 or 1 mg) overcame the Phen block of ovulation. Control hamsters had peak levels of LH between 1400 and 1800 h and a biphasic release of FSH consisting of a peak at 1600 h on proestrus, a return to basal levels at 2200 h, and a second more sustained surge between 2400 and 0800 h on the morning of estrus. Phen completely depressed the proestrous surge of both gonadotropins but only partially inhibited the second FSH elevation on the morning of estrus. In ovulatory animals, P alone or combined with 1 or 10 mug E2 restored peak LH levels at 1600 h. FSH levels on proestrus in hamsters treated with Phen plus P peaked at 1800 h, while the addition of 1 mug E2 resulted in increased FSH levels at 1600 h; peak levels in both groups were about half of control values. No proestrous increase was detected in ovulatory animals treated with P and 10 mug E2. FSH levels on estrus in hamsters injected with P alone or in combination with E2 were intermediate between those of controls and animals given Phen only. Levels of LH and FSH in animals treated with a single or double dose of Phen or Phen plus E2 or T were not different during the periovulatory period.

Effects of FSH and LH on incorporation of [3H]thymidine into follicular DNA

“…The (Zarrow, Yochim & McCarthy, 1964 Bast & Greenwald (1974) for the hamster and LH was assayed by an ovine-ovine assay method described previously (Siegel et al, 1976). The gonadotrophin concentrations were expressed in terms of NIAMDD rat FSH-RP-1 (21 NIH-FSH-Sl) and rat LH-RP-2 (003 NIH-LH-S1), respectively.…”

“…The follicles were classified into 10 stages based on histological criteria: Stages \-<\ consist of 1-4 layers of granulosa cells; Stage 5 has 5-6 layers of granulosa cells with early formation of thecal cells at the 6 layered follicle; Stage 6 has 7-8 layers of granulosa cells; Stage 7 shows incipient development of an antral cavity; Stages 8-10 are small, intermediate and large changes during the periovulatory period suggested that fluctuations in blood gonadotrophin con¬ centrations might not only account for the recruitment of the next set of follicles destined to ovulate but also stimulate the growth of small preantral follicles. The present study was designed to test this possibility by using hamsters in which ovulation was blocked by injecting phenobarbitone at the onset of the critical period on the day of pro-oestrus (Siegel, Bast & Greenwald, 1976), which were hypophysectomized and subsequently treated with FSH (Moore & Greenwald, 1974) and those which were unilaterally ovariectomized (Bast & Greenwald, 1977).…”

Quantitative analysis of in-vitro incorporation of [3H]thymidine into hamster follicles during the oestrous cycle

“…(Bast & Greenwald, 1974). Beginning at 22:00 h on Day 4, there is an increase in serum FSH, accompanied by low levels of LH, which is sustained throughout the afternoon of Day 1 (Siegel, Bast & Greenwald, 1976 (Peluso & Steger, 1978) and causes follicular recruitment in the rat (Hoak & Schwartz, 1980) and in the hamster (Greenwald, 1975;Greenwald & Siegel, 1982). Eshkol & Pariente (1984) have shown that FSH significantly stimulates [3H]thymidine incorporation in rat granulosa cells in culture while hCG has no effect.…”

The neuroendocrine control of clock-timed gonadotropin release in the female Syrian hamster: role of serotonin

“…To conserve animals, blood was collected from unanesthetized animals at 1330 h by cardiac puncture and at 1700 h by decapitation. This methodology has been used to obtain serial reproductive hormone measurements from Syrian hamsters in our laboratory (Stetson et al 1981, Donham et al 1984, 1994, Talamantes et al 1984, Donham & Stetson 1985 as well as other laboratories (Siegel et al 1976, Siegal & Greenwald 1978, Terranova & Greenwald 1979, Jorgenson & Schwartz 1987. We chose to collect blood from unanesthetized animals since commonly used anesthetics perturb hormone levels.…”