Pregnant Mare Serum Gonadotropin Treatment Research Articles

Effect of chronic alcohol consumption on the pregnant mare serum gonadotropin-induced luteinizing hormone surge.

The studies reported in this paper were undertaken to investigate the effect of chronic (10 day) alcohol consumption on female pituitary-gonadal function. The immature female rat model treated with pregnant mare serum gonadotropin (PMSG) was used since it results in a highly reproducible luteinizing hormone (LH) surge and ovulation. Twenty-day-old female rats were placed on diets that were either (1) unrestricted (ad libitum); (2) contained 5% ethanol in a liquid diet, or (3) isocalorically pair-fed with the liquid diet to the ethanol group. After 10 days on their respective diets, the groups were subdivided and given either 8 IU of PMSG in 0.1 ml saline or 0.1 ml saline s.c. between 10.00 and 11.00 h. The animals were sacrificed by decapitation at 24, 48, 52, 54, 56, 58, 60 and 62 h after injection. Trunk blood was obtained for serum measurements of LH. The uteri were weighed and prepared for the histological study. In all dietary groups, serum LH levels were significantly higher in the PMSG-treated animals when compared to the saline controls at all time intervals with the exception of the alcohol 58-hour group. In the ad libitum animals, plasma LH concentrations were highest at 52 h following hormone administration. The serum LH concentrations were highest at 56 h after hormone administration in the pair-fed group and were significantly less than the ad libitum group at 52, 54, 56, and 58 h after PMSG stimulation. No significant plasma LH surge was observed in the alcohol group and the LH concentrations were significantly less than the pair-fed rats at 56 and 58 h after PMSG treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Partial denervation of the ovaries by transection of the suspensory ligament does not inhibit ovulation in rats treated with pregnant mare serum gonadotropin.

Adrenergic nerves reach the ovary via two routes: along the arteries to the ovary and via the suspensory ligament. Results from earlier investigations suggest that denervation of the nerves along the arteries does not influence the ovulatory process. In the present study we have examined whether denervation by transection of the ovarian suspensory ligament influences the ovulatory process. Partial denervation of the ovary by transection of the ovarian suspensory ligament, sham operation, or only anesthesia were performed on immature 25-day-old rats. To induce ovulation, pregnant mare serum gonadotropin (PMSG) was injected in the morning (0800-0930), when the rats were 26 days old. This PMSG treatment normally induces ovulation around 0200 in the early morning of day 29 with subsequent formation of corpora lutea. Rats were killed 5-8 hr, 3 days, and 5 days after this ovulation time. Ovarian interstitial norepinephrine levels were markedly decreased after transection of the suspensory ligament. Ovulations had occurred in all denervated, as well as sham-operated, and control rats. The various groups did not differ in the number of ovulations per rat. Thus, the adrenergic nerves in the suspensory ligament appear not to be necessary for ovulation. Whether catecholamines themselves play a role in the ovulatory process cannot be elucidated from this experiment, since the norepinephrine content in the ovary was not totally depleted. It seems unlikely that adrenergic nerves reach the corpus luteum via the suspensory ligament, since transection of this structure did not change the luteal content of norepinephrine.

Ovarian cyclic GMP concentration and guanylate cyclase activity in immature rats after treatment with pregnant mare serum gonadotrophin.

We have previously reported that the LH-induced decrease in the concentration of ovarian cyclic GMP (cGMP) in the rabbit was accompanied by a drop in ovarian guanylate cyclase activity. The present experiments were carried out to see if the increase in cGMP concentration that occurs in immature rat ovaries after stimulation with pregnant mare serum gonadotrophin (PMSG) is also accompanied by changes in guanylate cyclase activity. Total ovarian cGMP, along with ovarian weight, was found to be increased at 16 h after PMSG treatment. Ovarian concentrations of cGMP, however, increased only after that period (at 20, 24 and 48 h) and the increase was progressive. Guanylate cyclase activity was found in both the cytosol and 100 000 g particulate fractions of the immature rat ovaries. Forty-three hours after PMSG treatment, activity in the particulate fraction was found to be significantly increased. This increase in guanylate cyclase activity was also found at 20 h but not at 16 h. Thus, the increase in ovarian cGMP concentration in immature rats after PMSG treatment was accompanied by increased guanylate cyclase activity.

A comparison of PMSG and LHRH agonist treatment in the induction of ovulation in the anoestrous ewe

The aim of this experiment was to compare the use of pregnant mares' serum gonadotrophin (PMSG) with that of a luteinizing hormone releasing hormone (LHRH) agonist in the induction of ovulation in anoestrous sheep. Anoestrous ewes were treated with progestagen-impregnated sponges for 12 days. They were given either PMSG at the time of sponge withdrawal or the LHRH agonist D-Ser(But) 6desGlyNH 2 10LHRH ethylamide 20 h after sponge withdrawal. This protocol was followed over 2 consecutive years. Plasma concentrations of oestradiol and LH were measured, and in the first year a comparison was made of the ovulation rate, conception rate and luteal function of the two groups after artificial insemination. During the first year, all of the PMSG-treated group but none of the agonist-treated group exhibited oestrus. Five of the eight PMSG-treated ewes had embryos in utero at slaughter whilst none was present in the agonist-treated ewes. The secretion of progesterone was greatest in the PMSG-treated ewes ( P < 0.001). During the second year, a more frequent blood-sampling regime was employed. Increased plasma concentrations of LH occurred within 3 h of agonist administration. Plasma oestradiol concentrations peaked at 20 h and 45 h after sponge withdrawal in both groups. Both peaks were larger in the agonist-treated group. It is concluded that a single dose of the highly potent LHRH agonist is unable to produce normal luteal function or conception using the present protocol.

Selective release of follicle-stimulating hormone and luteinizing hormone by 5 alpha-dihydroprogesterone and 3 alpha, 5 alpha-tetrahydroprogesterone in pregnant mare's serum gonadotropin-primed immature rats exposed to constant light.

The effects of 5 alpha-dihydroprogesterone (5 alpha-DHP) and 3 alpha, 5 alpha-tetrahydroprogesterone (3 alpha, 5 alpha-THP) on follicle-stimulating hormone (FSH) and luteinizing hormone (LH) release were examined in the pregnant mare's serum gonadotropin (PMSG)-primed immature female rat (8 IU PMSG at 28 days of age) maintained in constant light. Control rats kept in 14L:10D conditions exhibited proestrous-like surges of LH and FSH release with peak levels attained at 1800 h on the second day after PMSG treatment. In rats exposed to constant light, the PMSG-induced surges of LH and FSH were not only delayed until 1000 h on the third day after PMSG, resulting in a delay in ovulation, but were also significantly attenuated when compared to the gonadotropin surges that occurred on Day 2 in rats kept under normal light-dark conditions. The administration of 5 alpha-DHP significantly enhanced the release of FSH at 1000 h on Day 3 when compared to constant light-exposed controls, but had no effect on LH. Treatment with 3 alpha, 5 alpha-THP selectively potentiated the release of LH at 1000 h on Day 3 and had an attenuating effect on FSH release on Days 2 and 3. These observations confirm earlier findings in the immature ovariectomized estrogen-primed rat and suggest that 5 alpha-DHP and 3 alpha, 5 alpha-THP may have significant roles in the regulation of FSH and LH secretion.

Effects of pregnant mare serum gonadotrophin and oestradiol benzoate on enzymes associated with xenobiotic metabolism in immature and hypophysectomized female rats.

Treatment of immature (22-day-old) female Sprague-Dawley rats with pregnant mare serum gonadotrophin (PMSG) resulted in a significant increase in hepatic microsomal cytochrome P-450 concentrations when compared with animals treated with 0.9% (w/v) NaCl solution. Cytochrome P-450 concentrations in microsomes from control and PMSG-treated animals were 0.49 +/- 0.07 and 0.78 +/- 0.18 nmol/mg microsomal protein respectively (mean +/- S.D.). When hypophysectomized rats were treated with PMSG no significant difference was observed between saline-treated and PMSG-treated animals (0.84 +/- 0.06 vs 0.88 +/- 0.08 nmol/mg microsomal protein). Cytochrome b5 concentration and NADPH-cytochrome c reductase and ferricyanide reductase activities were not significantly affected by PMSG treatment. Similar results were obtained when immature and hypophysectomized rats were treated with oestradiol benzoate. Hepatic glutathione (GSH) S-transferase activity was significantly stimulated over control values when hypophysectomized or immature animals were treated with PMSG, oestradiol benzoate or 3-methylcholanthrene. Treatment of animals simultaneously with PMSG or oestradiol benzoate and 3-methylcholanthrene resulted in higher transferase activity than did either treatment alone. Oestradiol benzoate or PMSG treatment of immature female rats resulted in an approximate twofold increase in hepatic aryl hydrocarbon hydroxylase (AHH) activity. However, AHH activity in hypophysectomized animals was not significantly increased by PMSG or oestradiol benzoate treatment. It is concluded that PMSG or oestradiol benzoate treatment of immature female rats resulted in increased total cytochrome P-450 concentration and AHH activity in hepatic microsomes. Glutathione S-transferase activity was also stimulated. Neither PMSG nor oestradiol benzoate stimulated cytochrome P-450 levels or AHH activity in hypophysectomized rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Ovarian response to PMSG treatment in ewes immunized against oestradiol-17 beta.

The effects of active immunization against oestradiol-17 beta on the ovarian response to pregnant mare serum gonadotrophin (PMSG) was investigated in Merino ewes. Immunized (79) and control (41) ewes were synchronized with intravaginal sponges, given either 750 or 1500 i.u. PMSG and then mated to rams or inseminated laparoscopically with fresh diluted semen. All control ewes mated naturally exhibited oestrus and 40 out of 41 control ewes ovulated. The ovulation rate was higher in the controls receiving 1500 i.u. PMSG than in those ewes which received 750 i.u. PMSG (10.2 v. 3.3). Immunization against oestradiol-17 beta resulted in antibody titres varying from 100 to more than 100 000 in plasma taken 1-4 days after mating. The ovarian response increased significantly in the lowest titre group (100-1000) in conjunction with stimulation with 1500 i.u. PMSG. In these ewes the ovulation rate increased over controls (16.7 v. 10.2) as did the total ovarian response, which includes follicles greater than 10 mm diameter (22.3 v. 11.1). The total ovarian response was also increased in those ewes given 750 i.u. PMSG which had titres in the 1000-10 000 and 10 000-100 000 range, but this was not accompanied by significant increases in the ovulation rate. In general, the higher titre levels (greater than 1000) were correlated with decreases in the proportion of ewes showing oestrus and ovulating and in the embryo recovery rate. The 1500 i.u. PMSG treatment group with the highest titres (greater than 10 000) also showed a significant drop in the ovulation rate as compared to the 1500 i.u. PMSG controls.

INFLUENCE OF BREED ON THE REPRODUCTIVE PERFORMANCE OF EWES TREATED WITH FLUOROGESTONE-ACETATE-IMPREGNATED INTRAVAGINAL SPONGE AND PREGNANT MARE'S SERUM GONADOTROPHIN DURING THE BREEDING SEASON

The influence of breed on the reproductive performance of 454 mature ewes treated with fluorogestone acetate (FGA)-impregnated intravaginal sponges and pregnant mare's serum gonadotrophin (PMSG) to induce synchronized estrus during the breeding season was studied from 1978 to 1980 at a single location under field conditions. Fertility and fecundity after breeding at the synchronized estrus were, respectively, 79 and 145% for Polled Dorset, 51 and 94% for Suffolk, and 65 and 113% for North Country Cheviot breeds. The fertility and fecundity of the Polled Dorset were significantly higher than those of the Suffolk, but the North Country Cheviot was not significantly different from Polled Dorset and Suffolk breeds. There was no significant difference among the breeds with respect to prolificacy. Significant year-to-year variation in fertility and fecundity, but not in prolificacy, was observed among breeds with respect to FGA-PMSG treatment at the synchronized estrus. We conclude that the use of FGA-impregnated intravaginal sponge and PMSG treatment with appropriate breeds of sheep may further enhance the reproductive outcome of breeding at the synchronized estrus during the breeding season. Key words: Breeds, sheep, FGA sponge, PMSG, reproduction

Ultrastructural alterations associated with the initiation of follicular atresia.

To identify and describe ovarian follicles committed to undergo follicular degeneration (atresia), immature rats were primed with pregnant mare serum gonadotropin (PMSG). After PMSG treatment, preovulatory follicles develop but subsequently degenerate. Prior to the appearance of pyknotic nuclei (Stage I of atresia), degenerative changes were observed in focal areas of the granulosa cell layer. These changes include "blebbing" of the cytoplasm and alterations in the shape of the granulosa cells. The appearance of these degenerative changes coincides with a decrease in ovarian concentrations of estradiol and testosterone. Since estrogens and androgens maintain the follicle, the decline in estradiol and testosterone could be responsible for the further degenerative alterations that lead to complete deterioration of the preovulatory follicle. In Stage I atretic follicles, lysosome-derived autophagic vacuoles develop and macrophages invade both the thecal and granulosa cell layers. The combined actions of the autophagic vacuoles and macrophages could destroy both the granulosa-cell and thecal layers and thereby transform the preovulatory follicle into an ovarian cyst.

SUPEROVULATION AND SUPERPREGNANCY IN THE GOLDEN HAMSTER.

Pregnant mare serum gonadotropin (PMSG) treatment given in the morning or afternoon on any day of the four-day estrous cycle and human chorionic gonado tropin (HCG) given two days later successfully induced superovulation in the golden hamster. The minimum interval between PMSG and HCG necessary to obtain consistent superovulation was approximately 44 hr. The lowest ovulation rate was obtained following PMSG treatment on the afternoon of day 4 despite the fact that this time coincides with the maximum endogenous FSH level, necessary for the maturation of the next crop of follicles destined to ovulate. Thirty-eight to one-hundred percent of superovulated females in four different treatment groups became superpregnant after natural mating. Some treated females exhibited two consecutive nights of estrus with ovulation apparently occurring during the second night. Superpregnant females delivered "super" size litters, up to 27 live-born pups. The ultimate litter size appeared to be established after day 3 and prior to day 8 of superpregnancy. A one-day extension of the normal 16-day gestation period was observed in 31% of superpregnancies. Unilateral pregnancies were observed at autopsy in 44% of treated females which received the high dose of PMSG (30 IU). The progeny of superovulated females reproduced normally at maturity. The results indicate that ova from superovulated female hamsters are capable of full normal development.

The effect of pregnant mare serum gonadotropin on mouse oocytes as monitored at metaphase II

Ovulated oocytes were collected from random-bred, 7–12 week old ICR mice injected with 0, 3, or 6 i.u. pregnant mare serum gonadotropin (PMSG). Analyses of 872 metaphase figures from 87 females did not show a significant increase in chromosomal imbalance with PMSG treatment. A tendency toward ovum fragmentation was noted with an increase in PMSG dose.

Pre-ovulatory changes in cyclic AMP and prostaglandin concentrations in follicular fluid of gilts

The concentrations of cyclic adenosine 3′,5′-monophosphate (cyclic AMP) and prostaglandins E and F (PGE and PGF) were determined in follicular fluid collected from follicles of prepubertal gilts at various times after treatment with pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG) to induce ovulation. The concentrations of cyclic AMP, PGE and PGF in the follicular fluid after PMSG treatment but prior to hCG injection were about 1 pmol/ml, 1 ng/ml and 0.2 ng/ml, respectively. After hCG administration, the follicular fluid levels of cyclic AMP increased markedly, reaching a peak (400-fold increase) about 4 h after injection and then declined gradually to pre-hCG levels. A second rise (2.5- to 5-fold increase) occurred about 30 h after hCG with the levels being sustained up to the expected time of ovulation. In contrast, the levels of PGE and PGF remained relatively constant until 28–30 h after hCG treatment. Thereafter, the concentrations of both prostaglandins began to rise with the increases becoming more pronounced and reaching maximal values as the expected time of ovulation approached. These data provide further evidence for a physiological role of follicular prostaglandins in the process of ovulation but do not support an obligatory role for prostaglandins in the acute gonadotropin stimulation of cyclic AMP formation.

Inhibition of maturation of isolated rat oocytes by porcine follicular fluid.

The inhibitory action of porcine follicular fluid (FF1) on the spontaneous maturation of isolated rat oocytes was studied. Both FF1 and a low-molecular-weight fraction thereof (PFF1) inhibited the maturation of oocytes in culture. When the oocytes were scrutinized for maturation after culturing for 6 h in a medium containing 50% (v/v) FF1, the incidence of germinal vesicle breakdown (GVB) was reduced from 75 to 53% (P &lt; 0·001) in oocytes collected 20 h after administration of pregnant mare serum gonadotrophin (PMSG), and from 94 to 53% (P &lt; 0·01) in oocytes collected from preovulatory follicles 44 h after treatment with PMSG. Prolongation of the culture period to 20 h resulted in an increase in the number of oocytes undergoing GVB to 58% (harvested 20 h after PMSG treatment; P &lt; 0·001) or 71% (44 h after treatment with PMSG; P &gt; 0·05). Inhibition of GVB by PFF1 occurred at concentrations ≥ 0·085 mg protein/ml; the extent of inhibition was related directly to the concentration of inhibitor and inversely to the duration of culture and the developmental stage of the follicles from which the oocytes were derived. The inhibition of the resumption of meiosis by FF1 or PFF1 was overcome by ovine LH (5 μg/ml). However, GVB was delayed even in the presence of LH, compared with controls cultured in the absence of the inhibitor. These results demonstrate that the maturation-inhibiting action of porcine follicular fluid is not species specific and that the sensitivity of the rat oocyte to the inhibitor changes during the course of follicular development.

Effects of Hypophysectomy on the Functions of Ovarian Mitochondria of Mature Rats

SummarySteroidogenic activity and oxi-dative phosphorylation were measured in ovarian mitochondria of intact mature rats, hypophysectomized mature rats and gonad-otropic-treated, hypophysectomized mature rats to determine the dependence of these parameters on gonadotropic stimulation. Mitochondrial cholesterol oxygenase activity was not detectable in ovarian preparations of hypophysectomized rats, but increased dramatically 54 hr after treatment with 40 IU of pregnant mare serum gonado-tropin (PMSG). In contrast, specific cyto-chrome oxidase activities were similar in mitochondria of all three experimental groups. With both glutamate and succinate as substrates, the ADP:O ratio of ovarian mitochondria of hypophysectomized rats increased significantly over that of mitochondria of intact rats. PMSG treatment of hypophysectomized rats returned the ADP:O ratio to the value observed in intact rats. The succinate oxidation rate of ovarian mitochondria of hypophysectomized rats was significantly greater than tho...

Ovarian Responsiveness to Exogenous Gonadotropins During Lactation in the Rat and Monkey

During lactation, the normal function of the ovary in the rat and monkey is generally suppressed. Ovarian refractoriness to gonadotropins as a possible causative factor in lactational amenorrhea was tested in the present study. The increase in serum and ovarian steroid levels and the induction of ovulation following pregnant mare serum gonadotropin (PMSG) and ovine luteinizing hormone (LH) supplementation were used for assessing ovarian function. In the rat, the response of the ovary to PMSG was shown to be dependent upon the intensity of the suckling stimulus—the greater the intensity, the lower the responsiveness. Rats suckling a minimal number of pups also showed lowered responsiveness if ovine prolactin were given along with PMSG. Following PMSG and ovine LH treatment, lactating monkeys showed increases in serum estrogen and progesterone levels. The injection of ovine prolactin appeared to reduce ovarian responsiveness to PMSG in terms of estrogen production. In contrast, ovine prolactin given with ovine LH (when administered as an ovulation trigger) appeared to facilitate progesterone production from the primate corpus luteum. These results suggest that during lactation the ovary continues to respond to gonadotropins, although the response is reduced.

ANTERIOR PITUITARY SENSITIVITY IN IMMATURE FEMALE RATS STIMULATED WITH GONADOTROPHIN RELEASING HORMONE IN VIVO: EFFECT OF PRIMING WITH OESTROGEN, PREGNANT MARE SERUM GONADOTROPHIN OR BRAIN LESION

An investigation of pituitary sensitivity, assessed in terms of increments in plasma LH and FSH concentrations, to stimulation with one or two injections of gonadotrophin releasing hormone (GnRH) was carried out on 26-day-old immature female rats which had received one of the following priming treatments: 10 μg oestradiol benzoate (OB) as a single injection on day 23 or day 25, or on both days; 10 i.u. pregnant mare serum gonadotrophin (PMSG) on day 24; an electrochemical brain lesion placed in the mediobasal hypothalamus on day 23; control animals received either vehicle alone or a sham lesion. Pituitary sensitivity assessed at 10.00 h on day 26, after one or two injections of GnRH (100 ng/100 g body weight, s.c.), was enhanced to a similar degree in the three groups treated with OB in terms of LH (P &lt; 0-01). The FSH response also increased after OB treatment but was not statistically significant. In contrast, 48 h after the injection of PMSG (i.e. when the rats were in a 'pro-oestrous-like' condition) pituitary sensitivity in terms of both LH and FSH dropped sharply (P &lt; 0·001). In lesioned animals, pituitary sensitivity to one injection of GnRH was unchanged. A second GnRH injection administered after a 60 min interval induced a slightly larger LH response in control animals. In contrast, the ratio of the second response to the first increased in animals treated with PMSG, despite the state of overall decrease in sensitivity, being 4·5:1 in PMSG-treated rats versus 1·4:1 in controls. In a second set of experiments, we investigated the variation of pituitary sensitivity in conjunction with an experimentally induced gonadotrophin surge. In animals treated with OB on day 23 and with 1 mg progesterone at 12·00 h on day 26, pituitary sensitivity was increased at both 14.00 and 17.00 h as compared with that in the day 23 OB-treated group at 10.00 h. The PMSG-treated animals maintained their state of decreased responsiveness at 14.00 h, but exhibited increased pituitary sensitivity at the time of the gonadotrophin surge (17.00 h). These results show that OB increases pituitary sensitivity to GnRH in 26-day-old female rats and that the induction of a gonadotrophin surge further increases this sensitivity. In contrast, PMSG-treated rats displayed a state of decreased responsiveness 48 and 52 h, but not 55 h, after the injection. Pituitary sensitivity on the second day after PMSG treatment thus clearly differs from that observed during pro-oestrus in the adult cyclic female rat.

Studies on Oxidative Phosphorylation and Steroidogenesis by Ovarian Mitochondria after Gonadotropic Stimulation

No differences in oxidative phosphorylation or in the per cent of [4-14C]progesterone were found in ovarian mitochondria of immature rats after treatment with 20 IU of pregnant mare serum gonadotropin (PMSG) iv 30 min before killing. However, treatment of immature rats with 20 IU of PMSG sc 54 h prior to killing decreased the ADP:O ratio and increased the per cent of [4-14C]cholesterol conversion. Electron microscopic studies showed that mitochondria with lamellar cristae were prominent in ovaries of untreated rats, while large pleomorphic mitochondria and mitochondria with tubulovesicular cristae dominated in ovaries of PMSG-treated rats. Ovarian homogenates separated by zonal centrifugation showed three peaks od cytochrome oxidase activity which shifted to the heavier end of the gradient after PMSG treatment. These studies suggest that PMSG treatment influences ovarian mitochondria, possibly by stimulating the synthesis of additional functional components and/or the biogenesis of new mitochondria. Aminoglutethimide addition to bovine luteal mitochondria decreased steroidogenesis by 60% when succinate was used as substrate. However, there was a 16% increase in the ADP:O ratio, apparently due to a decrease in oxygen utilization. When oligomycin was added to luteal mitochondria, there was a 30% decrease in the ACP:O ratio but a 300% increase in [4-14C]cholesterol conversion. Dinitrophenol also decreased mitochondrial steroidogenesis. These results suggest that energy obtained from succinate oxidation can be diverted from phosphorylation to support steroidogenesis.

Effect of temperature and pregnant mare's serum gonadotropin on testicular function in the spiny-tailed lizard, Uromastix hardwicki

The effect of temperature and pregnant mare's serum gonadotropin (PMSG) was observed on the testes of Uromastix hardwicki at a time of the year (November) when the seminiferous epithelium contained abundant proliferating spermatogonia and some primary spermatocytes. This recrudescent state of the testes was maintained by keeping the animals at 20° for 10 days. But, in lizards kept at 35°, there was a marked decrease in the testis weight. The seminiferous tubules were lined mostly with Sertoli cells and a few resting types of spermatogonia. The interstitial cells were only slightly affected and there was no reduction in androgen concentrations in the testicular tissue or plasma, as measured by testosterone radioimmunoassay. At 20°, injections of 20 IU of PMSG daily for 10 days induced an increase in the number of primary spermatocytes and production of spermatids in certain regions of the tubules. In the PMSG-treated lizards kept at 35° the testes contained a single layer of resting spermatogonia placed along the basement membrane. Under these conditions PMSG failed to maintain the active state of the seminiferous epithelium. Unlike the germinal cells, the interstitial cells were markedly stimulated by PMSG at 20 or 35°. Testicular and plasma androgen levels were increased severalfold in gonadotropin-treated lizards. The elevation of androgen levels as a result of PMSG stimulation was higher in lizards kept at 35°. It is suggested that in Uromastix hardwicki, the germinal epithelium responds differentially to PMSG treatment at the two different temperatures and that the activity of the interstitial cells is not inhibited by hyperthermia.

Actions of Pregnant Mare Serum Gonadotropin in the Immature Female Rat: Correlative Changes in Blood Steroids, Gonadotropins, and Cytoplasmic Estradiol Receptors of the Anterior Pituitary and Hypothalamus11

Several blood steroids, serum gonadotropins and cytosol estradiol receptors of the anterior pituitary and hypothalamus were quantified in immature female rats which were induced to ovulate with pregnant mare's serum gonadotropin (PMSG). Studies revealed that serum levels of progesterone, 17-hydroxyprogesterone, testosterone, androstenedione and estradiol were initially elevated at 6 PM (day 30) after administration of 8 IU of PMSG at 10 AM day 30. Serum levels of estradiol and testosterone rose progressively from day 30 through the AM of day 32. A further increase in serum concentrations of progesterone, 17-hydroxyprogesterone, androstenedione, testosterone, and dehydroepiandrosterone occurred on the PM of day 32 whereas serum estradiol levels declined. Serum levels of all steroids declined on the day of estrus (33) and only progesterone levels were further elevated on day 34 (diestrus). Dihydrotestosterone concentrations were minimally altered by PMSG treatment. Saline administration resulted in no significant alterations in levels of any steroid quantified from day 29 to 34 in control animals. A progressive decline in cytosol estradiol receptor content of the anterior pituitary and hypothalamus was documented following PMSG treatment of intact female rats; there was no depletion of receptors following PMSG administration to ovariectomized immature rats. Maximal depletion of cytosol estradiol receptors occurred on day 32 with replenishment of cytosol estradiol receptor levels on estrus (day 33). The preovulatory gonadotropin surge was found to occur on the PM of day 32 after maximal receptor depletion. The cycle of depletion and replenishment of receptors was repeated during a second spontaneous estrous cycle four days later which coincided with a rise and fall in serum estradiol levels. It is suggested that the depletion of cytosol estradiol receptors of the anterior pituitary/hypothalamic unit may be causally related to the preovulatory gonadotropin surge resulting from PMSG administration to immature female rats. In addition, changes in blood steroids and gonadotropins after PMSG treatment are similar to those reported for proestrus-estrus-diestrus I of the normal adult estrous cycle. These findings further demonstrate the validity of the PMSG-primed immature female rat preparation as a model for the estrous cycle of the adult rat.

Egg transfer in the bovine: Effect of injecting PMSG on different days

Sixty one (61) donor animals were inoculated with 500 I.U./100 kg body-weight of Pregnant Mare Serum Gonadotropin (PMSG) on days 9–14 of their oestrous cycle and given 25 mg PGF 2α 48 hrs. later. The superovulatory response to the PMSG injection on different days were evaluated based on the number of corpora lutea (CL) present in both ovaries at the time of surgical ova collection 5 days after standing heat. The average number of CL's was 11,1. The highest number of CL's was observed when PMSG was injected on day 11 (12,5 ± 5,5) and the lowest following day 14 treatment (4,5 ± 3,2). No statistical difference was found between days 9–10–11, 12 and 13. The results suggest that a certain “day of injection variation” may exist and contribute to the umpredictability of PMSG treatments.