Hr Of Proestrus Research Articles

ETHANOL-INDUCED ALTERATIONS IN GONADOTROPHINS SECRETION DURING THE ESTROUS CYCLE OF RATS

The effects of ethanol administration during a preovulatory period on both serum and pituitary gonadotrophin concentrations were studied in female rats. The animals were injected with 2 g/kg of ethanol (30% v/v, in saline solution) at 18:00 hr of diestrous 2. Hormonal levels were measured by RIA at different times during the estrous cycle, especially during the proestrus day. The preovulatory LH surge was inhibited using ethanol. Serum LH levels decreased between 16.00 and 20.00 hr of proestrus (P < 0.01). The levels of FSH in serum were slightly depressed by ethanol between 12.00 and 17.00 hr of proestrus (P < 0.05 with respect to the control set), but the values during the proestrus surge (18.00-20.00 hr) were unaffected. Ethanol augmented pituitary hormonal content during the periods in which serum hormonal levels decreased (P < 0.05 with respect to the control set) but it did not affect gonadotrophins synthesis. The increase in pituitary gonadotrophin concentrations induced by ethanol during the proestrus day is due to the accumulation of the hormone which was not released before. The preovulatory LH surge was re-established in the next cycle (5th day after treatment). These effects of ethanol on gonadotrophin levels could explain the previously observed anovulatory effects induced by ethanol administration in diestrous.

Quantitative changes in ovarian 17 alpha-hydroxylase/C17,20-lyase and aromatase activities during the estrous cycle of the hamster.

Aromatase activity of the microsomal fraction of ovarian homogenates, measured by a tritium exchange assay using androstenedione (A-dione) as substrate, did not change during the 4-day estrous cycle of the hamster. In contrast, 17 alpha-hydroxylase, measured by a tritium exchange assay with progesterone as substrate, and particularly C17,20-lyase activity, evaluated by acetic acid production from progesterone, drastically decreased on the afternoon of proestrus (Day 4). The latter two activities remained low on Days 1 and 2 but increased dramatically on Day 3 and the morning of Day 4. The serum concentration of A-dione and 17-hydroxyprogesterone reached a peak at 1600 hr of proestrus and then decreased rapidly as the enzyme activities decreased. A-dione levels were undetectable on Day 1 but 17-hydroxyprogesterone levels remained elevated through Day 2. The results are consistent with the view that 17 alpha-hydroxylase and C17,20-lyase are activities of a single cytochrome P-450, as has been shown for testis and adrenal. Increases in hydroxylase and lyase activities occur concomitantly with decreases in the serum concentrations of progesterone, suggesting that the latter steroid may play a role in controlling these enzymes.

Reproductive/endocrine and anaphylactoid properties of an LHRH-antagonist, ORF 18260 [Ac-DNAL 1(2),4FDPhe 2,D-Trp 3,D-Arg 6]-GnRH

It has been demonstrated in a variety of experiments that ORF 18260 inhibits (ED 100) spontaneous and LHRH-induced ovulation in rats (10 μg/kg s.c.; 10 mg/kg i.g.) and hamsters (100 μg/kg s.c. and 100 mg/kg i.g.). Inhibition of LHRH induced ovulation appears to be competitive in nature. In normally cycling animals, efficacy varies with time of administration. In the spontaneously ovulating rat, the most effective time is 15.00 hr of proestrus; in the hamster it is 10.00 hr. Continuous administration inhibits ovulation in rats, and ORF 18260 has contragestational activity in rats and hamsters but not in guinea pigs and mice. Prostate growth in rats is inhibited at a dose of 100 μg/kg (s.c.). Our studies also suggest that ORF 18260 can also induce cutaneous anaphylactoid-like reactions in rats. When compound is administered intradermally in rats, ORF 18260 causes a dose-related whealing response, noticeable from the 0.01 μg/rat dose level.

Is the First or Second Periovulatory Surge of FSH Responsible for Follicular Recruitment in the Hamster?

AbstractProestrous hamsters were injected at 1300 hr with phenobarbital to block ovulation. The animals were bled via cardiac puncture every 6 hr beginning at 1600 hr of proestrus until 1000 hr of estrus. The ovaries were then removed and a quantitative evaluation of follicular development carried out. In saline-injected proestrous hamsters, there was a peak of serum FSH and LH at 1600 hr followed by a second prolonged peak of FSH at 0400 and 1000 hr of estrus accompanied by low tonic levels of LH. This hormone profile was associated at 1000 hr of estrus with an average of 9.3 large preantral follicles (stage IV follicles) per ovary. In contrast, the phenobarbital-treated hamsters showed no increases in either gonadotropin at any time and the ovaries contained large antral follicles and an average of only 1.7 stage IV follicles per ovary (three of four animals). Injection of 1 mg progesterone concurrent with phenobarbital restored the first surge of LH but not FSH and partially restored the second peak of...

Plasma and pituitary concentrations of LH, FSH, and Prolactin in aging C57BL/6 mice at various times of the estrous cycle

—Plasma and pituitary concentrations of LH, FSH, and prolactin (Prl) were measured by RIA in 2–4, 7–8, 12–13 and 16–20 month-old female C57BL/6 mice during various stages of the estrous cycle. In general, gonadotropin concentrations tended to rise with increasing age and Prl concentrations tended to decline. Pronounced differences existed, however, between the four age groups around the time of the LH surge. LH secretion declined progressively with increasing age at 21.00 hr of proestrus. Aged mice, 16–20 months old, had significantly lower plasma concentrations of LH than did other age groups. It is not known whether age-related changes in the ovary, pituitary, or hypothalamus are largely responsible for differences in the secretion of LH, FSH and Prl in aging C57BL/6 mice.

Adrenal and Ovarian Steroid Secretion in the Rat Estrous Cycle Temporally Related to Gonadotropins and Steroid Levels Found in Peripheral Plasma

This study was undertaken to determine the patterns of estrogen and progestin secretion by the adrenal and the ovary and to relate these to the levels of steroids and gonadotropins found in peripheral plasma. A total of 70 rats were used in this study. Adrenal venous (ADVB) and ovarian venous blood (OVB) were collected by concurrent cannulation and peripheral blood (PB) was obtained from the abdominal aorta. Estrone (E1), estradiol (E2), PROGESTERONE (P) and 17alpha-hydroxyprogesterone (17alpha-OHP) were measured by radioimmunoassay. The concentration of E2 in general was higher in ADVB than in OVB. Although increased levels of E2 in ADVB were found on the afternoon of proestrus (1527-2634 pg/ml), they were not significantly different from those recorded at other times. In contrast E2 in OVB was lowest at 1000-1200 hr of estrus (225 pg/ml) and highest at 1000-2000 hr of proestrus (1190-1605 pg/ml). The E2 in PB followed the pattern seen in OVB; the values ranged from 80-211 pg/ml. P concentration in general was higher in ADVB than in OVB. The lowest concentration of P in ADVB was between 0200-0400 hr of estrus (183 ng/ml) and the highest between 1400-1600 hr of proestrus (580 ng/ml) and 1000-1200 hr of estrus (591 ng/ml). The lowest concentration of P in the OVB was between 1600-1800 hr of diestrus (42 ng/ml) and the highest between 0200-0400 hr of estrus (466 ng/ml). In the PB, P reflected changes in adrenal as well as ovarian secretion; the values ranged fron 7-25 ng/ml. E1 in ADVB was in general lower than in OVB, and there were no significant changes at any stage of the cycle. In the OVB, however, E1 showed a pattern similar to that of E2. Levels of E1 in PB were very low and failed to show any significant changes. 17alpha-OHP was high in ADVB, although there were no significant changes during the cycle; PB levels also did not show any significant changes. In the OVB a peak of 17alpha-OHP was recorded between 0200-0400 hr on the day of estrus. The LH and FSH levels showed increases after 1600 hr on the day of proestrus and this was in agreement with earlier studies. Since the adrenal secretes all of the 4 steroids studied, it is reasonable to assume that it does exert some effect in the pituitary-gonadal axis. A role of adrenal P for the facilitation of the preovulatory LH release has been indicated and the increased secretion of adrenal P between 1400-1600 hr of proestrus supports this possibility.