Effects of luteinizing hormone on superovulatory and steroidogenic responses of rat ovaries to infusion with follicle-stimulating hormone

Immature female rats were infused s.c. continuously over a 60-h period with a partially purified porcine pituitary follicle-stimulating hormone (FSH) preparation having FSH activity 4.2 x NIH-FSH-S1 and luteinizing hormone (LH) activity 0.022 x NIH-LH-S1. High rates of superovulation were observed in rats receiving 1 U FSH/day, with 69 +/- 11 oocytes/rat recovered as cumulus-enclosed oocytes from oviducts on Day 1 (equivalent to the day of estrus). Addition of LH to the FSH, at dosages equivalent to 2.5-100 micrograms/day NIH-LH-S1 equivalents (2.5-100 mU) resulted in a dose-related inhibition of superovulation, reaching a nadir of 15 +/- 7 oocytes recovered from rats receiving 50 mU LH/day together with 1 U FSH/day. At the two highest LH doses, 50 and 100 mU/day, ovulation was advanced so that 12 +/- 3 and 15 +/- 4 oocytes, respectively, were recovered from oviducts of these rats flushed on the morning of Day 0, compared to none in rats infused with FSH alone. Ovarian steroid concentrations (ng/mg) observed on the morning of Day 0 in rats infused with FSH alone were progesterone, 0.50 +/- 0.13; testosterone, 0.16 +/- 0.08; androstenedione, 0.06; and estradiol, 0.23 +/- 0.05. On the morning of Day 1, ovarian progesterone concentrations in rats infused with FSH alone had risen to 3.30 +/- 0.33 ng/mg, whereas concentrations of testosterone, androstenedione, and estradiol, had fallen to essentially undetectable levels. Addition of LH to the FSH infusion resulted in dose-related increases, on Day 0, of all four steroids up to a dosage of 25 mU LH/day. At higher LH dosages, Day 0 ovarian concentrations of androgens and estradiol fell markedly, while progesterone concentrations continued to increase. Histological examination of ovaries revealed increases in the extent of luteinization of granulosa cells in follicles with retained oocytes on both Days 0 and 1 in rats infused with 25 and 50 mU LH/day together with 1 U FSH/day, compared to those observed in rats receiving FSH alone. These findings indicate that the elevated progesterone levels on Day 0 and inhibition of ovulation observed at these LH doses were due to premature luteinization of follicles, thus preventing ovulation. At lower LH doses, no sign (based on histologic or steroidogenic criteria) of premature luteinization was evident, suggesting that the decreased superovulation in these rats was due to decreased follicular maturation and/or increased atresia rather than to luteinization of follicles without ovulation.(ABSTRACT TRUNCATED AT 400 WORDS)     

Superovulation of immature rats by continuous infusion of follicle-stimulating hormone

Immature female rats were infused s.c. continuously over a 60-h period with partially purified porcine pituitary follicle-stimulating hormone (FSH) preparations differing in degree of purity and having widely divergent luteinizing hormone (LH):FSH potency ratios as defined by radioreceptor assays. Rats infused with the more purified FSH preparation (FSH-A) ovulated a mean of 60-85 oocytes per rat on the morning of the third day (Day 1) after FSH infusion was begun (on Day -2). The same total dose of FSH administered as a single s.c. injection or as twice daily injections over the same 60-h period resulted in ovulation in only a minority of treated rats (3/16), with none achieving ovulation rates approaching those of rats infused continuously. High fertilization rates (80% of ovulated oocytes) were observed in superovulated rats joined with fertile males on the evening of the second day of infusion (Day 0). Of the 67 +/- 7 fertilized ova per rat retrieved from oviducts flushed on Day 1, 52 +/- 8, or 80%, were accounted for as morulae or blastocysts recovered when oviducts and uteri were flushed on the morning of Day 5, demonstrating essentially normal developmental rates and high survival rates in reproductive tracts of superovulated females during the preimplantation period. Infusion of rats with the same dose of a less well-purified FSH preparation (FSH-E) containing 20 times as much LH activity, or injection of rats with a superovulatory dose of pregnant mare's serum gonadotropin (PMSG) (40 IU), were much less effective in causing superovulation, with ovulation rates of 17 +/- 6 and 34 +/- 8 oocytes/rat, respectively, compared to 79 +/- 9 oocytes/rat infused with the FSH preparation (FSH-A) containing lower LH activity.(ABSTRACT TRUNCATED AT 250 WORDS)     

The superovulation of synchronous adult rats using follicle-stimulating hormone delivered by continuous infusion

The estrous cycles of adult female rats were synchronized with an LHRH agonist on the morning of Day -4 (Day 0 = day of mating). On Day -2, animals received s.c. implants of continuous-infusion osmotic minipumps containing different doses of an FSH preparation (Folltropin) in combination with hCG at various ratios of hCG:FSH or were given single injections of eCG in doses ranging from 15 IU to 60 IU. Rats infused with the optimal dose (3.4 U/day) of FSH ovulated 44.1 +/- 5.4 oocytes/rat while rats treated with the most effective dose (60 IU) of eCG ovulated only 20.5 +/- 4.3 oocytes/rat on the morning of Day 1. The inclusion of hCG in pumps at ratios from 0.188:1 to 0.75:1 (hCG:FSH) had no significant effect on ovulation rate. The importance of synchronization of estrus in successful superovulation was demonstrated by the finding that only 70% of the unsynchronized animals ovulated (29.1 +/- 4.8 oocytes/rat) whereas 95% of the synchronized animals ovulated (51.0 +/- 3.6 oocytes/rat). Oocyte viabilities were assessed by determining fertilization rates and embryonic development in vivo following mating with fertile males. In rats superovulated by use of the FSH regimen, 92% (39.0 +/- 4.1) of the recovered embryos were 1-cell zygotes on Day 1, 89% (36.3 +/- 5.6) were at the 2-cell embryo stage of development on Day 2, and 88% (28.8 +/- 2.2) were at the morula and blastocyst stages on Day 5 following mating on Day 0. The high ovulation rates and oocyte viability in rats receiving infusions of Folltropin following estrus synchronization offer a reliable method for superovulation of adult rats.     

FSH-induced ovulation in intact and hypophysectomized mice

A single, ovulatory dose of 25 micrograms of a highly purified preparation of ovine FSH caused ovulation in 89% of hypophysectomized and 91% of intact female mice primed 48 h earlier with PMSG; the number of oocytes recovered (29.4 +/- 4.7 and 22 +/- 2.7/mouse ovulating, respectively) compared favourably with the 20.0 +/- 2.9 oocytes per ovulating female recovered from animals that received PMSG + hCG. After oFSH injection, 82% of oocytes released were fertilized and developed to blastocysts. That the trace contamination (less than 0.2%) of the oFSH with oLH was not responsible for the ovulation was shown by the markedly reduced number of oocytes collected from ovulating females that were injected with equivalent low levels of hCG (0.001 micrograms) or oLH (1 microgram) (9.0 +/- 3.3 and 8.0 +/- 3.1, respectively). These results demonstrate that oFSH is as effective as LH in inducing ovulation of competent oocytes in the mouse.     

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.     

Gonadotropin-releasing hormone treatment induces follicular growth and ovulation in seasonally anestrous mares

A study was conducted to evaluate the effectiveness of gonadotropin-releasing hormone (GnRH) pulse infusion to stimulate follicular development and induce ovulation in seasonally anestrous standardbred mares. Seventeen mares were selected for use in this experiment, on the basis of a previous normal reproductive history, and were housed under a photoperiod of 8L:16D beginning one week prior to the start of the experiment (second week in January). Mares were infused with 20 micrograms (n = 7) or 2 micrograms (n = 6) GnRH/h, or were subjected to photoperiod treatment only (controls, n = 4). Serum concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and progesterone did not vary, and neither significant follicular development nor ovulation was observed in any control mare throughout the experimental period (greater than 60 days). By contrast, both groups of GnRH-treated mares showed elevated serum concentrations of LH and FSH within one day after the start of infusion. Mares infused with 20 micrograms GnRH/h had at least one follicle greater than or equal to 25 mm in 7.4 +/- 1.3 (mean +/- SEM) days following the start of infusion, and ovulated in 12.0 +/- 0.7 days. In the 2-microgram-GnRH/h treatment group, a 25-mm follicle was detected in 5.7 +/- 0.7 days, and ovulation occurred after 10.0 +/- 0.3 days of infusion. Ovulation in every instance was followed by a functional luteal phase, as indicated by the profiles of progesterone secretion.(ABSTRACT TRUNCATED AT 250 WORDS)     

Differential regulation of the secretion of luteinizing hormone and follicle-stimulating hormone around the time of ovulation in the bitch

Plasma concentrations of luteinizing hormone (LH) and follicle stimulating hormone (FSH) were determined 3-6 times daily in six Beagle bitches from the start of the follicular phase until 5 d after the estimated day of ovulation. The aim of the study was to gain more detailed information regarding the changes in and the temporal relation between these hormones around the time of ovulation. In all bitches, the pre-ovulatory LH surge was accompanied by a pre-ovulatory FSH surge. The mean duration of the pre-ovulatory FSH surge (110 +/- 8 h) was significantly longer than that of the pre-ovulatory LH surge (36 +/- 5 h). The FSH surge started concomitantly with the pre-ovulatory LH surge in four bitches, and 12 h before the start of the LH surge in the other two bitches. The pre-ovulatory LH surge had a bifurcated pattern in four bitches. The mean plasma LH concentration before (1.9 +/- 0.4 microg/L) and after (1.9 +/- 0.3 microg/L) the pre-ovulatory LH surge were similar. The mean plasma FSH concentration during the period 72-28 h before the pre-ovulatory LH surge (1.6 +/- 0.3 U/L) was lower (P < 0.001) than that during the period 100-144 h after the pre-ovulatory LH surge (3.1 +/- 0.2U/L). In conclusion, this study demonstrated concurrent pre-ovulatory surges of FSH and LH and provided more evidence for differential regulation of the secretion of FSH and LH.     

Continuous subcutaneous infusion of human menopausal gonadotropin in anovulatory women with decreased FSH/LH ratio and androgen excess

Ten women of polycystic ovarian-type (PCO-type) anovulation, having a decreased ratio of FSH to LH and androgen excess, resistant to the previous clomiphene, bromocriptine and/or daily im injections of human menopausal gonadotropine (hMG), were treated with continuous sc infusion of 150 IU/day hMG. The treatment was initiated on cycle day 2-5 and continued until the dominant follicle reached 20 mm or more in diameter, when an im bolus of 10,000 IU human chorionic gonadotropin was given. The treatment elevated the geometric mean of pretreatment serum FSH (8.6 mIU/ml) to 15.9 mIU/ml (p less than 0.001), while serum LH decreased from 29.4 mIU/ml to 20.7 mIU/ml (p less than 0.01). This resulted in a highly significant increase in the FSH/LH ratio from 0.29 to 0.77 (p less than 0.0001). Follicle enlargement was demonstrated in 13 of the 14 treatment cycles, 12 of which were ovulatory. Pregnancy ensued in 4 cases, 1 of which was a quadruplet pregnancy. Continuous infusion of hMG was indicated as an effective way of inducing ovulation in PCO-type anovulation resistant to conventional methods of ovulation induction.     

Preimplantation embryo development and serum steroid levels in immature rats induced to ovulate or superovulate with pregnant mares' serum gonadotropin injection or follicle-stimulating hormone infusions

Follicular stimulation protocols using pregnant mares' serum gonadotropin (PMSG) or a follicle-stimulating hormone (FSH) preparation were compared to evaluate the yield and quality of embryos obtained from immature rats. Rats received a superovulatory dose of PMSG (401U), a nonsuperovulatory dose of the same gonadotrophin (4 IU), or a continu ous s.c. infusion over a 72-h period with a purified FSH preparation containing an opti mum ratio of luteinizing hormone (LH): FSH (FSH-hCG). The females were caged with fertile males on the evening of the 3rd day of gonadotropin treatment and scored for the occurrence of mating on the next morning; subgroups were killed on days 1–4 of preg-nancy. High fertilization rates were observed in rats treated with 4 IU PMSG (84.1%) and in rats infused with FSH-hCG (91.0%); however, a much lower fertilization rate was observed following treatment with 40 IU PMSG (41.5%). From median ovulation rates of 9 and 79 in rats treated with 4 IU PMSG and in rats infused with FSH-hCG, medians of 8 and 69 embryos, respectively, were recovered from reproductive tracts flushed on day 4 of pregnancy, from which 75% were morulae or blastocysts; in contrast, from a median ovu lation rate of 42.5, a median of only 12 embryos was recovered on day 3 of pregnancy following superovulation with 40 IU PMSG of which 80% were degenerate ova. Serum steroid profiles during the first 4 days of pregnancy differed significantly among treatment groups, the major differences being in substantially elevated levels of estradiol and andro-gens on days 1–3 in rats receiving the high (40 IU) dose of PMSG. Levels of these steroids in rats superovulated with the FSH-hCG infusion regimen were only marginally elevated above levels observed in rats treated with the low (4 IU) nonsuperovulatory dose of PMSG. Consistent with high ovulation rates, serum progesterone levels rose to considera bly higher levels during the period in both superovulated groups than in animals receiving the low, nonsuperovulatory dose of PMSG. This work describes a novel method to superovulate rate (FSH-hCG) leading to high yields of normally developing embryos at all preimplantation stages and illustrates the close association between high yield of emyryos and low levels of circulating andorgens and estradiol-17β during the preimplantation period.     

Effect of various agents on ovarian plasminogen activator activity during ovulation in pregnant mare's serum gonadotropin-primed immature rats

The plasminogen activator/plasmin synthetic substrate S-2251 was used to measure the effect of indomethacin, cycloheximide, colchicine, dexamethasone, tranexamic acid, and aprotinin on the elevation of ovarian plasminogen activator (PA) that normally occurs during ovulation in the rat. Young Wistar rats were weaned on the morning of Day 21, given 4.0 IU of pregnant mare's serum gonadotropin (PMSG) s.c. at 0800 h on Day 22, and given 10.0 IU of human chorionic gonadotropin (hCG) on Day 24. These animals normally began ovulating between 0000 and 0200 h on Day 25. The induced ovulation rate was 11.5 +/- 2.2 ova/rat, based on the number of ova in the oviducts of control animals at 0900 h on Day 25. In the controls, PA activity in extracts of homogenized ovaries increased 3-fold from 0.125 +/- 0.010 OD units just before the administration of hCG to 0.371 +/- 0.021 at 12 h after hCG, i.e., near the time of ovulation. Indomethacin, in doses of 0.1-1.0 mg/rat, inhibited ovulation but did not inhibit the normal increase in PA activity, whereas indomethacin at the high dose of 10.0 mg/rat inhibited both ovulation and PA activity. Cycloheximide, at a dose of 0.1 mg/rat, was given at 12 h before hCG, immediately after hCG, and at 9 h after hCG. This agent inhibited ovulation most effectively when given at 12 h before hCG, yet it inhibited PA activity most effectively when given immediately after or at 9 h after hCG. Colchicine, at a dose of 0.1 mg/rat, inhibited ovulation, but not PA activity, when it was given 1 h before hCG.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of methodology for administration of porcine FSH for use in estrus induction and for increasing ovulation rate in prepubertal gilts

Ovulation rate influences production efficiency of oocytes and embryos and depends upon the amount of gonadotropin administered and the ratio of FSH:LH activity. In Experiment 1, gilts (n=135) were assigned to receive 10 or 15 Armour units (AU) of porcine FSH containing 6%, 10%, or 15% LH, whereas controls received PG600. Gilts received 1/6th the FSH dose in six sc administrations at 8-h intervals. There was no treatment effect on incidence of estrus (66%) or cysts (23.9%), or number of corpora lutea (CL, 29.6). However, treatment did affect the percentage of gilts ovulating (P<0.05) with fewer 10 AU FSH with 15% LH-treated gilts ovulating (15%) compared to controls (72%), whereas the other treatments did not differ (range, 44-65%). Experiment 2 tested whether FSH in polyvinlypyrrolidinone (PVP) could induce estrus and ovulation with reduced administration frequency. Gilts (n=105) were assigned to receive 15 AU FSH with 10% LH in one (1P) or two sc administrations (2P) whereas controls received PG600. There was no treatment effect on incidence of estrus (64%) or cysts (22%). However, the percentage of gilts ovulating was lower for 1P (56%), but did not differ (P<0.05) between 2P (83%) and controls (85%). Treatment influenced ovulation rate (P<0.05) with 2P having more CL (24) than controls (12) and 1P (19). Results indicated that 10 and 15 AU FSH induced estrus and ovulation, although high LH content proved detrimental. Further, 15 AU FSH with 10% LH in PVP allowed for reduced administration frequency without compromising ovulation.     

Effect of phenoxybenzamine on luteinizing hormone release in the female rat

To clarify the mode of action of phenoxybenzamine, an alpha adrenergic blocking agent, its effects upon plasma LH levels in ovariectomized rats and upon the ovulatory LH surge expected between 1400 and 1600, the critical period, on the day of proestrus in normal rats were studied. A single injection of phenoxybenzamine, 20 mg/kg, given at 1300 on the day of proestrus bokced ovulation (1 out of 7 ovulating), while plasma LH did not differ from controls between 1500 and 1600. An additional injection of 20 iu HCG at 1500 prevented the ovulation block (83% ovulating). A single phenoxybenzamine injection at 1700 failed to prevent ovulation (5 out of 7 ovulating). The beta adrenergic blocking agents, propanolol and MJ 1999, did not affect ovulation. Treatment with phenoxybenzamine for 2 days, 20mg/kg/day, for 8 days, 10mg/kg/day, were did not prevent the rise causing a reduction in blood flow through the ovary rather than acting as a neurogenic stimulus in the hypothalamus.     

Pulsatile administration of gonadotropin-releasing hormone advances ovulation in cycling mares

Cycling standardbred mares were infused with saline or 20 micrograms gonadotropin-releasing hormone (GnRH) in a pulsatile pattern (one 5-sec pulse/h, 2 h or 4 h) beginning on Day 16 of the estrous cycle. Although serum concentrations of luteinizing hormone (LH) increased significantly earlier in all three GnRH-treated groups (within one day of the initiation of infusion) compared to saline-infused controls, there were no differences in peak periovulatory LH concentrations among treatments (overall mean +/- SEM, 8.98 +/- 0.55 ng/ml). The number of days from the start of treatment to ovulation was significantly less in mares infused with 20 micrograms GnRH/h (mean +/- SEM, 2.9 +/- 0.6 days after the initiation of treatment, or 18.9 days from the previous ovulation; N = 7) compared to mares treated with saline (5.9 +/- 0.3 days, or 21.9 days from previous ovulation; N = 7) or 20 micrograms GnRH per 4 h (5.4 +/- 0.9 days or 21.4 days from previous ovulation; N = 5). Although mares infused with 20 micrograms GnRH/2 h ovulated after 4.3 +/- 0.7 days of treatment (Day 20.3; N = 7), this was not significantly different from either the control or 20 micrograms GnRH/h treatment groups. Neither the duration of the resulting luteal phase nor the length of the estrous cycle was different between any of the treatment groups (combined means, 14.7 +/- 0.2 days and 21.3 +/- 0.4 days, respectively). We conclude that pulsatile infusion of GnRH is effective in advancing the time of ovulation in cycling mares, but that the frequency of pulse infusion is a critical variable.     

The aging Leydig cell: 1. Testosterone and adenosine 3',5'-monophosphate responses to gonadotropin stimulation in rats

Plasma testosterone levels before and after a single injection of hCG were significantly lower in 24-month old rats than 60--90 day old animals (p less than 0.001). Even with repeated hCG administration for three weeks, plasma testosterone levels of old rats could not be restored to levels present in unstimulated young rats. In response to in vitro LH and 8-bromo-cyclic AMP stimulation, purified young Leydig cells produced significantly higher amounts of testosterone than Leydig cells from old rats. Maximal testosterone formation of the young Leydig cells in response to LH was 42.0 +/- 6.88 ng/10(6) cells, while cells from old rats produced only 16.8 +/- 3.69 ng/10(6) cells (p less than 0.01). However, the dose of LH at which one half maximal response (ED50) occurred was 0.1 mIU/ml for young Leydig cells and 0.05 mIU/ml for old Leydig cells. Basal and 1.0 mIU LH-stimulated cyclic AMP formation were comparable in both groups, but cyclic AMP formation in response to 10 mIU of LH was significantly less in the old rats (p less than 0.05). Present results demonstrate impaired steroidogenic capacity of old rats both in vivo and in vitro. Decreased testosterone response in old rats most likely is the consequence of understimulation of Leydig cells by gonadotropin; however, there appear to be additional intrinsic defects in old Leydig cells.     

Effects of aromatizable and nonaromatizable androgen treatments on luteinizing hormone receptors and ovulation induction in immature rats

The effects of androgen pretreatment on follicle-stimulating hormone (FSH)-stimulated luteinizing hormone (LH) receptor induction in ovarian granulosa cells was examined. Immature female rats were treated with various doses (0.1-5 mg/rat) of testosterone (T), 5 alpha-dihydrotestosterone (DHT), 5 alpha-androstane-3 alpha,17 beta-diol (3 alpha-diol), or 5 alpha-androstane-3 beta,17 beta-diol (3 beta-diol). Subsequent follicular development was stimulated by treatment with ovine FSH. LH receptor induction in granulosa cells and ovulatory responses to 10 IU human chorionic gonadotropin (hCG) were examined. Since LH receptor induction requires the synergistic action of both FSH and estradiol, the effects of the androgen pretreatment on FSH-stimulated estradiol production were also examined. Dihydrotestosterone treatment at doses greater than 1 mg inhibited LH receptor induction by approximately 70%, which resulted in absent ovulatory responses. Treatment with 1 mg or more of T or 3 alpha-diol had no effect on LH receptor induction, yet the hCG-stimulated ovulation rate was reduced to 40% of that seen in vehicle-treated controls. 3 beta-Diol, at a dose of 1 mg/rat, did not affect LH receptor induction but did reduce hCG-stimulated ovulation responses. No significant effects of androgen treatment on ovarian or uterine weight or FSH-stimulated estradiol production were observed. These results suggest that androgens can act at multiple sites to inhibit ovarian follicular development and function. In addition these studies demonstrate that, although LH receptor induction is necessary, it may not be a sufficient condition to ensure ovulation of ovarian follicles.     

Temporal relations between plasma concentrations of luteinizing hormone, follicle-stimulating hormone, estradiol-17beta, progesterone, prolactin, and alpha-melanocyte-stimulating hormone during the follicular, ovulatory, and early luteal phase in the bitch

Compared with other domestic animals, relatively little is known about the changes in, and temporal relations between, reproductive hormones around the time of ovulation in the domestic bitch. Therefore, plasma concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), estradiol-17beta, progesterone, prolactin (PRL), and alpha-melanocyte-stimulating hormone (alpha-MSH) were determined one to six times daily from the start of the follicular phase until 5 days after the estimated day of ovulation in six Beagle bitches. In all bitches, the pre-ovulatory LH surge was accompanied by a pre-ovulatory FSH surge. A pre-ovulatory PRL or alpha-MSH surge was not observed. The pre-ovulatory FSH and LH surges started concomitantly in four bitches, but in two bitches the FSH surge started 12 h earlier than the LH surge. The FSH surge (110+/-8 h) lasted significantly longer than the LH surge (36+/-5 h). In contrast with the pre-ovulatory FSH surge, the pre-ovulatory LH surge was bifurcated in four of six bitches. The mean plasma LH concentrations before (1.9+/-0.4 microg/L) and after (1.9+/-0.3 microg/L) the LH surge were similar, but the mean plasma FSH concentration before the FSH surge (1.6+/-0.3 U/L) was significantly lower than that after the FSH surge (3.1+/-0.2 U/L). In most bitches the highest plasma estradiol-17beta concentration coincided with or followed the start of the pre-ovulatory LH surge. In five of the six bitches the plasma progesterone concentration started to rise just before or concurrently with the start of the LH surge. In conclusion, the results of this study provide evidence for the differential regulation of the secretion of LH and FSH in the bitch. In addition, the interrelationship of the plasma profiles of estradiol-17beta and LH suggests a positive feedback effect of estradiol-17beta on LH surge release. The start of the pre-ovulatory LH surge is associated with an increase in the plasma progesterone concentration in this species.     

The effect of the presence and pattern of luteinizing hormone stimulation on ovulatory follicle development in sheep

The aim of this study was to examine the role of LH on the growth of the large preovulatory follicle and its secretion of hormones in sheep. Ewes with ovarian autotransplants were treated with GnRH-antagonist at the time of luteal regression and different LH regimes applied for 60-66 h before administration of an ovulatory stimulus (hCG). In Experiment 1 (N = 24; n = 8), ewes received either no LH or constant or pulsatile infusion of LH at the same dose (1.25 microg/h). In Experiment 2 (N = 12, n = 6), LH was constantly infused at a rate of 1.25 microg or 2.5 microg oLH/h. In Experiment 1, animals receiving either pulsatile or constant LH exhibited increases in estradiol and inhibin A secretion (P < 0.001) and a depression in FSH (P < 0.001) that resembled the normal follicular phase. Similarly in Experiment 2, doubling the dose of LH resulted in a two-fold increase in ovarian estradiol secretion (P < 0.05) but no other changes. All animals receiving LH, regardless of the pattern of stimulation, ovulated and established a normal luteal phase. In contrast, no LH treatment resulted in constant immuno-active LH without pulses, unchanged FSH and inhibin A concentrations (P < 0.05), and basal estradiol secretion (P < 0.001). Morphologically normal large antral follicles were observed in this group and although corpora lutea formed in response to hCG, progesterone profiles were abnormal. In conclusion, these results suggest that LH is an essential requirement for normal ovulatory follicle development and subsequent luteal function and show that a pulsatile mode of LH stimulation is not required by ovulatory follicles.     

Factors attenuating growth promoting effect of growth hormone therapy for Turner's syndrome

Nine patients with Turner's syndrome aged 7 to 13 years were treated with recombinant human growth hormone (hGH) at a dose of 0.5 or 1.0 U/kg/w for 1 year. In five of them the growth rate was accelerated from 3.3 +/- 0.6 (SD) to 6.5 +/- 0.5 cm/y (group A), whereas 4 had a reduced rate of growth promotion (3.4 +/- 0.3 to 4.6 +/- 0.4 cm/y) (group B). Analysis of factors affecting growth response to hGH revealed 3 major parameters: (1) age of initiating hGH therapy (A, 9.5 +/- 2.1 vs B, 13.3 +/- 0.4 yrs, P less than 0.01), (2) basal LH (A, 3.2 +/- 2.4 vs, B, 44.9 +/- 17.8 mIU/ml, P less than 0.001) and FSH levels (A, 14.7 +/- 15.4 vs B, 131 +/- 49 mIU/ml; P less than 0.01) and (3) somatomedin-C (SM-C) producing capacity: coefficient of correlation to growth rate, r = 0.80, P less than 0.01). No remarkable changes were observed in the results of glucose tolerance, thyroid state, calcium metabolism and liver function tests. These results indicate that patient's age is the most crucial factor in effective treatment with hGH, and in adolescent girls, gonadal failure with a limited increase in SM-C production attenuates the growth promoting potency of hGH.     

Amino-terminal leucine-rich repeats in gonadotropin receptors determine hormone selectivity.

Recombinant expression of truncated receptors for luteinizing hormone/chorionic gonadotropin (LH/CG) revealed that the amino-terminal leucine-rich repeats 1-8 of the extracellular receptor domain bind human chorionic gonadotropin (hCG) with an affinity (Kd = 0.72 +/- 0.2 nM) similar to that of the native LH/CG receptor (Kd = 0.48 +/- 0.05 nM). LH/CG receptor leucine-rich repeats 1-8 were used to replace homologous sequences in the closely related receptor for follicle stimulating hormone (FSH). Cells expressing such chimeric LH/CG-FSH receptors bind hCG and show elevated cylic AMP levels when stimulated by hCG but not by recombinant human FSH (rhFSH). Similarly, a chimeric LH/CG receptor in which leucine-rich repeats 1-11 originated from the FSH receptor is activated by rhFSH but not by hCG. For this chimera, no residual [125I] hCG binding was observed in a range of 2 pM to 10 nM. Our results demonstrate that specificity of gonadotropin receptors is determined by a high affinity hormone binding site formed by the amino-terminal leucine-rich receptor repeats.     

Effect of gonadotropin-releasing hormone antagonists on serum follicle-stimulating hormone and luteinizing hormone under conditions of singular follicle-stimulating hormone secretion

Previous work has indicated that in long-term ovariectomized rats a potent antagonist to gonadotropin-releasing hormone (GnRH) suppressed serum luteinizing hormone (LH) more successfully than follicle-stimulating hormone (FSH). The present studies examined whether the rise in serum FSH which occurs acutely after ovariectomy, or during the proestrous secondary surge, depends on GnRH. In Experiment A, rats were ovariectomized at 0800 h of metestrus and injected with (Ac-dehydro-Pro1, pCl-D-Phe2, D-Trp3,6, NaMeLeu7)-GnRH (Antag-I) at 1200 h of the same day, or 2 or 5 days later. Antag-I blocked the LH response completely, but only partially suppressed serum FSH levels. Experiment B tested a higher dose of a more potent antagonist [( Ac-3-Pro1, pF-D-Phe2, D-Trp3,6]-GnRH; Antag-II) injected at the time of ovariectomy. The analog suppressed serum LH by 79% and FSH by 30%. Experiment C examined the effect of Antag-II on the day of proestrus on the spontaneous secondary surge of FSH, as well as on a secondary FSH surge which can be induced by exogenous LH. Antag-II, given at 1200 h proestrus, blocked ovulation and the LH surge expected at 1830 h, as well as increases in serum FSH which occur at 1830 h and at 0400 h. Exogenous LH triggered a rise in FSH in rats suppressed by Antag-II. In Experiment D proestrous rats were injected with Antag-II at 1200 h and ovariectomized at 1530 h. By 0400 h the antag had suppressed FSH in controls, but in the ovariectomized rats, a vigorous FSH response occurred.(ABSTRACT TRUNCATED AT 250 WORDS)