Human chorionic gonadotropin and luteinizing hormone-releasing hormone reverse the blockade of ovulation in pregnant mare's serum gonadotropin-primed immature rats by the anti-androgenic drug, hydroxyflutamide

The present study was designed to examine mechanism(s) of the anti-ovulatory action of the anti-androgen, hydroxyflutamide (OH-F). Prepubertal rats were treated with 4 IU pregnant mare's serum gonadotropin (PMSG) (day -2) to induce first estrus and ovulation. They received OH-F in sesame oil or oil alone at 08:00 and 20:00 h on day 0 (the day of proestrus) and ovulations were assessed on the morning of day 1. Eighty-three percent of control animals ovulated with a mean of 7.7 +/- 1.1 corpora lutea per rat. Hydroxyflutamide blocked ovulation in all but 2 of the 12 rats receiving this drug alone. All of OH-F treated rats that received 5 and 25 IU human chorionic gonadotropin (hCG) ovulated with means +/- SEM of 9.1 +/- 0.1 and 7.3 +/- 1.4 corpora lutea per rat, respectively. The dose of 0.2 IU hCG was essentially ineffective, while the effect of 1.0 IU hCG was intermediate. At the dose of 20 ng and above (100 and 500 ng) luteining hormone-releasing hormone (LHRH) completely overcame the ovulation blockade in the OH-F treated animals, while a 4-ng dose was ineffective. At 18:00 h on the day of proestrus, serum LH levels in control animals were 17.56 +/- 2.60 ng/mL, which were 920% above basal levels (1.90 +/- 0.13) indicating a spontaneous LH surge. This surge was suppressed in OH-F treated rats. Injection of LHRH, at the dose of 20 ng and above, reinstated the LH release in OH-F treated animals. Thus, the anti-androgen, OH-F, inhibits ovulation in PMSG-treated immature rats through its interference with the preovulatory LH surge; the inhibition can be reversed by hCG or LHRH. Hydroxyflutamide does not appear to interfere at the level of the pituitary, but may have direct action at the hypothalamic and (or) extrahypothalamic sites involved in the generation of positive feedback signals that control LH release.     

Effect of pregnant mare's serum gonadotropin on increased ovulation in guinea pigs with synchronized estrous cycle

An ability of Pregnant Mare's Serum Gonadotropin (PMSG) to induce superovulation was investigated in guinea pigs with synchronized estrous cycle caused by the treatment for 21 days of progesterone tubing. On day 6 later following the removal of progesterone treatment, every animal given saline injection had synchronously ovulated. When compared with saline control, a significant increase of ova ovulated was induced by an injection of PMSG 8 hours before the removal of progesterone tubing, but not by the other PMSG treatment schedule. Present study indicates that PMSG injection given at a fixed stage of synchronized estrous cycle induced superovulation in guinea pigs treated with long-term implantation of progesterone tubing.     

Response of mouse ovaries in vivo and in organ culture to pregnant mare's serum gonadotrophin and human chorionic gonadotrophin

The effect of various doses of pregnant mare's serum gonadotropin (PMSG) and human chorionic gonadotropin (HCG) on the yield of oocytes undergoing preovulatory maturation in organ culture was studied in mice. The mice received ip injections of .5, 1, 3, or 5 IU PMSG and 48 hours later, 0, 1, 2, or 4 IU HCC or their ovaries were cultured with 0, .2, .4, or .8 IU HCG/ml. 3-5 IU PMSG by 1-2 IU HCG induced maximum preovulatory response both in vivo and in culture. The proportion of large antral follicles with oocytes at Metaphase 2 was lower in culture than in the intact animal. However, the number of preantral and small Graafian follicles increased to a higher level in vivo and thus the overall total number of oocytes that progressed beyond the germinal vesicle stage was higher in organ culture.     

Effect of super-ovulatory doses of pregnant mare serum gonadotropin and human chorionic gonadotropin in blastocyst implantation in golden hamsters

The effect of super-ovulatory dose of pregnant mare serum gonadotropin and human chorionic gonadotropin on ovulation, advancement of ovulation, subsequent embryo development and implantation were studied in the hamster. Groups of hamsters received pregnant mare serum gonadotropin injection on day 1 of the estrous cycle followed by human chorionic gonadotropin injection either at 56 or 76 h later, pregnant mare serum gonadotropin alone on day 1 or human chorionic gonadotropin alone on day 3.The combination therapy (pregnant mare serum gonadotropin and human chorionic gonadotropin) resulted in super-ovulation (an average of 40 mature ova/animal) while human chorionic gonadotropin alone yielded an average of 10 mature ova/animal. Ovulation was advanced by 24 h by giving human chorionic gonadotropin at 56 h instead of 76 h after pregnant mare serum gonadotropin. Subsequent embryo development and implantation occurring under different hormonal regimens were studied. The ova obtained by giving human chorionic gonadotropin injection at 56 h were poorly fertilizablein vivo and hence the pregnancy rate was low (6 %). These ova however, were fertilizablein vitro, suggesting that the low fertilization rate and developmental failure may be due to inhibition of sperm capacitation/transport because of premature human chorionic gonadotropin administration. In the group receiving human chorionic gonadotropin alone on day 3 there was fertilization and cleavage, but no implantation occurred due to failure of functional corpora lutea. However, administration of progesterone and estrone from day 2 of gestation resulted in 80% implantation and sustenance of pregnancy. On the other hand, the pregnant mare serum gonadotropin and human chorionic gonadotropin combination therapy resulted in super-pregnancy. The number of fetuses present at term was higher in the group receiving pregnant mare serum gonadotropin alone than in the group receiving the combination therapy. Embryo resorption however was higher (37%) in the latter group compared with the former (9.5%). However, preimplantation embryos were found to be viable as evidenced by fluorescein diacetate staining.     

Optimal dose of human chorionic gonadotropin for inducing ovulation in the ferret

The optimal dose of human chorionic gonadotropin (hCG) for induction of ovulation was determined by comparing the ovulatory response of 119 mated ferrets (controls) with that of estrous females induced to ovulate with five different dosages of hCG. Copulation induced formation of 12.7 ± 4.5 corpora lutea (CL) in all 119 females and resulted in a 90.7% conception rate as evidenced by finding approximately eight blastocysts/female in the uteri of 108 ferrets. All doses of hCG tested induced ovulation; however, the lower doses (50 and 75 IU) resulted in a lesser percentage of females ovulating. The highest doses of hCG (150 and 300 IU) resulted in fewer CL/female being formed. The optimal dose of hCG for simulating copulation induced ovulation was 100 IU. Tubal transport of unfertilized oocytes in pseudopregnant females was found to be significantly retarded when compared to the rate of transport of embryos in the control group.     

Induction of ovarian follicular cysts in the pregnant rat by human chorionic gonadotropin.

Prolonged stimulation by human chorionic gonadotropin (hCG) induces ovarian follicular cysts in progesterone-synchronized immature rats [Bogovich, Endocrinology 1989; 124:1646-1653]. To determine if unabated stimulation by hCG has a similar effect on follicular development in adult ovaries, pregnant rats were given either 0 (control), 1, or 3 IU hCG twice daily for 9 days beginning on Day 13 of pregnancy. By Day 22 of pregnancy, rats treated with 1 IU hCG possessed large antral follicles at least 1 mm in diameter: approximately 33% larger than the diameters of preovulatory follicles observed in control rats (0 IU hCG). In contrast, rats treated with 3 IU hCG displayed ovarian follicular cysts up to 5 mm in diameter, with well-developed thecae and just a remnant of granulosa cells. Progesterone, androstenedione, and estradiol accumulation was greater in follicular incubates from hCG-treated rats than in incubates from control rats. Progesterone increased in response to cAMP in incubates from all treatment groups on all days tested. Androstenedione increased in response to cAMP on Day 22 of pregnancy for follicles from control animals, on all days tested for follicles from rats treated with 1 IU hCG, and on Days 15-19 for follicles from rats treated with 3 IU hCG. Androstenedione production in the presence of 300 ng of exogenous testosterone was significantly greater in follicular incubates from animals treated with 1 and 3 IU hCG than incubates from control animals on Days 19-22 of pregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of a low dose of pregnant mare's serum gonadotropin on follicular recruitment and atresia in cycling rats

Atresia appears to play a central role in selecting the correct number of follicles for ovulation in the rat. A wave of atresia, apparent by noon on metestrus, reduces the number of large healthy follicles to the appropriate quota for ovulation. The purpose of this study was to test the hypothesis that falling levels of gonadotropin on the morning of estrus precipitate the wave of atresia of large follicles seen on metestrus. Endogenous concentrations of follicle-stimulating hormone (FSH) were augmented by a single injection of pregnant mare's serum gonadotropin (PMSG; 0.025 IU/gram body weight) administered at different times during the periovulatory period. Animals given PMSG at 0800 h on estrus (when the endogenous FSH surge was waning) had a supernormal number of large healthy follicles in their ovaries at 1200 h on metestrus. This increase in large healthy follicles was accompanied by a decrease in large atretic follicles in the ovaries. The same dose of PMSG, when administered at other times during the periovulatory period, did not affect any of the parameters measured. These observations suggest that the wave of atresia normally seen in large follicles on metestrus is triggered by the decline in the concentration of FSH during the morning of estrus and can be prevented by prolonging the surge of FSH with administration of PMSG.     

Effect of human chorionic gonadotropin on serum levels of progesterone and estrogens in the pregnant bonnet monkev (Macaca radiata)

Administration of human chorionic gonadotropin to pregnant bonnet monkeys(Macaca radiata) at 55–60 days and 130–140 days of pregnancy resulted in a significant increase in serum progesterone levels. This effect could be observed even in lutectomized monkeys. However, no significant change in the serum estrogen level was noticed. These results suggest that although no chorionic gonadotropin is detectable in the serum after 35 days of pregnancy, the foetoplacental steroidogenic system is still responsive to exogenous gonadotropic stimulation.     

Effects of in vivo crude human chorionic gonadotropin on ovulation and spawning of the African catfish, Clarias gariepinus Burchell–1822

The effects of increasing dosages of crude human chorionic gonadotropin (cHCG) on ovulation and spawning of Clarias gariepinus Burchell were examined. Four and 5 mg cHCG/100g body weight of fish gave the best response. The activation of the interrenals and stimulation of the ovary are discussed as a possible route of in vivo human chorionic gonadotropin administration on ovulation and spawning in catfish.