The role of protein synthesis in the stimulation by LH of prostaglandin accumulation in rat preovulatory follicles in vitro

Preovulatory follicles isolated from immature rats, treated $\text{in vivo}$ with pregnant mare's serum gonadotropin, were incubated $\text{in vitro}$ and the accumulation of prostaglandin E measured. The addition of luteinizing hormone (5 μg/ml) increased this accumulation, after a lag period of 3 hours. This delay suggested the involvement of macromolecular synthesis in the mechanism of prostaglandin stimulation by luteinizing hormone. When the synthesis of protein was inhibited by the addition of puromycin (100 μM), the luteinizing hormone stimulation of prostaglandin E in these follicles was completely abolished. This inhibition was not seen with an analogue of puromycin, which does not inhibit protein synthesis, puromycin amino-nucleoside. These data suggest that concomitant protein synthesis is required for the luteinizing hormone stimulation of prostaglandin accumulation in rat follicles.     

Effects of luteinizing hormone releasing hormone on gonadotrophins in the hamster

The changes in serum gonadotrophins in male hamsters following one injection of 15 μg luteinizing hormone releasing hormone (LHRH) (Group A) were compared with those following the last injection of LHRH in animals receiving an injection approximately every 12 hr for 4 days (Group B) or 12 days (Group C). Peak follicle stimulating hormone (FSH) levels (ng/ml) were 1776±218 (Group A), 2904±346 (Group B), and 4336±449 (Group C). Peak luteinizing hormone (LH) values (ng/ml) were 1352±80 (Group A), 410±12 (Group B), and 498±53 (Group C). Serum FSH:LH ratios, calculated from the concentrations measured 16 hr after the last LHRH injections, were higher in Groups B and C than in Group A. Similar injections of LHRH (100 ng or 15 μg/injection) for 6 days elevated the serum FSH:LH ratio in intact males. Five such LHRH injections (100 ng/injection) blunted the rise in serum LH in orchidectomized hamsters. Direct effects of LHRH on gonadotrophin secretory dynamics or altered brain-pituitary-testicular interactions may alter the ratio of FSH to LH in the hamster.     

Alteration in the normal pattern of serum testosterone and 5α-androstane-3α,17β-diol in the immature male rat following chronic treatment with luteinizing hormone releasing hormone or luteinizing hormone

A major component of sexual maturation in the male rat is a progressive decline in serum concentrations of 5α-androstane-3α,17β-diol (3α-diol) and a concomitant increase in testicular testosterone biosynthesis and secretion. Chronic administration of synthetic luteinizing hormone releasing hormone (LHRH) or luteinizing hormone (LH)/human chorionic gonadotropin (hCG) to immature male rats has been shown to result in a delay in sexual maturation as evidenced by decreased sex accessory gland weights and altered testicular testosterone production. We have examined the postulate that such treatments may either reverse or retard the normal developmental pattern of serum testosterone and 3α-diol concentrations. Chronic $\text{in vivo}$ treatment of 28 day old immature male rats for 2 weeks with daily injections of either 0.5 μg of LHRH, 1.0 μg of LHRH, or 30 μg of LH was found to result in significant reductions in weights of the seminal vesicles and ventral prostate glands and diminutions in serum testosterone concentrations. Serum content of 3α-diol was either unchanged or slightly elevated in the LHRH treated animals and increased significantly in the LH treated animals. These data suggest that either a reversal of or retardation in the normal developmental pattern of serum testosterone and 3α-diol content has been achieved in the immature male rat by chronic LHRH or LH treatment.     

Luteinizing hormone: Evidence for direct action in the CNS

This article is part of a Special Issue “SBN 2014”.Hormonal dysfunction due to aging, especially during menopause, plays a substantial role in cognitive decline as well as the progression and development of neurodegenerative diseases. The hypothalamic–pituitary–gonadal (HPG) axis has long been implicated in changes in behavior and neuronal morphology. Most notably, estrogens have proven beneficial in the healthy brain through a host of different mechanisms. Recently, luteinizing hormone (LH) has emerged as a candidate for further investigation for its role in the CNS. The basis of this is that both LH and the LH receptor are expressed in the brain, and serum levels of LH correlate with cognitive deficits and Alzheimer's disease (AD) incidence. The study of LH in cognition and AD primarily focuses on evaluating the effects of downregulation of this peptide. This literature has shown that decreasing peripheral LH, through a variety of pharmacological interventions, reduces cognitive deficits in ovariectomy and AD models. However, few studies have researched the direct actions of LH on neurons and glial cells. Here we summarize the role of luteinizing hormone in modulating cognition, and we propose a mechanism that underlies a role for brain LH in this process.     

蓝狐发情期及妊娠期血清五种生殖激素含量变化

为探究发情期及妊娠期雌性蓝狐(Alopex lagopus)生殖激素的变化规律,选取11只繁殖期雌性蓝狐,采用放射免疫法(RIA)测定血清中雌二醇(E2)、促黄体生成素(LH)、促卵泡素(FSH)、孕酮(P)以及催乳素(PRL)的含量。结果表明,促卵泡素和促黄体生成素在发情期及妊娠期血清中浓度一直处于较稳定水平,并呈波动式分泌,最大值分别为(2.18±0.69)U/L和(8.82±1.83)U/L,同种激素不同检测日期数据两两比较差异不显著(P> 0.05);雌二醇在发情期和妊娠期血清中浓度亦处于较稳定水平,最大值出现在发情第1天,为(27.73±23.19)ng/L,数据两两比较差异亦不显著(P> 0.05);孕酮在发情期维持较高水平,最大值在发情第3天,为(2.41±1.35)μg/L,之后在妊娠期持续下降,分娩当天达到最低点,为(0.13±0.14)μg/L,数据两两比较差异显著(P <0.05);催乳素在发情期先下降,最低值为(0.15±0.04)U/L,第3天开始升高,并在妊娠期保持较高水平,到分娩时维持最高(0.21±0.05)U/L,数据两两比较差异不显...     

Metabolism of GnRH in man: influence of estrogens

To clarify the influence of estrogens on the metabolism of gonadotropin-releasing hormone (GnRH), we studied the metabolic clearance rate (MCR) of GnRH (MCRGnRH), and the serum levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), estradiol and testosterone (total and free fraction) in 9 sexually mature men and 7 women under basal conditions and after treatment with the antiestrogen tamoxifen (2 X 10 mg/day p.o.) for 7 days. In women, the medication was started on day 7 +/- 1 of their menstrual cycles. To calculate the MCR, synthetic GnRH was continuously infused (1.53 micrograms/min) and its serum levels were measured by a radioimmunoassay. During tamoxifen treatment we observed a small but significant decrease in the MCR in men (455 +/- 48 to 357 +/- 46 ml/min/1.86 m2), whereas the known cyclic increase in the MCR in women was blunted (1,769 +/- 147 to 1,558 +/- 119 ml/min/1.86 m2). There was a small but significant increase in LH levels in women (8.3 +/- 2.1 to 11.5 +/- 2.5 mU/ml). LH and testosterone levels in men, and FSH and estradiol levels in both sexes did not change significantly. Conclusion: (1) estrogens regulate the MCRGnRH either directly or by changing gonadotropin levels, but the effect is only slight; (2) an enhanced metabolism of GnRH may contribute to the feedback of estrogens on the secretion of gonadotropins, and (3) the sex-specific difference of the MCR is presumably not caused by estrogens.     

Estrogen and LH dynamics during the follicular phase of the estrous cycle in the Asian elephant

Pituitary and corpus luteum hormone patterns throughout the elephant estrous cycle have been well characterized. By contrast, analysis of follicular maturation by measurement of circulating estrogens has been uninformative. This study tested the ability of a urinary estradiol‐3‐glucuronide radioimmunoassay to noninvasively assess follicular development during the nonluteal phase of the elephant estrous cycle, and to determine the relationship between estrogen production and the “double LH surge.” Daily urine and serum samples were collected throughout seven estrous cycles from three Asian elephants, and urine was collected from an additional three females, for a total of 13 cycles. Serum was analyzed for luteinizing hormone (LH), and urine was analyzed for estrogens and progestins. Elephants exhibited a typical LH pattern, with an anovulatory LH (anLH) surge occurring approximately 21 days before the ovulatory LH (ovLH) surge. The urinary estrogen pattern indicated the presence of two follicular waves during the nonluteal phase. The first wave (anovulatory) began 5 days before the anLH surge and reached a maximum concentration the day before the peak. Thereafter, urinary estrogens declined to baseline for 2 weeks before increasing again to peak concentrations on the day of the ovLH surge. Urinary progestins were baseline throughout most of the follicular phase, increasing 2–3 days before the ovLH surge and continuing into the luteal phase. These results support previous ultrasound observations that two waves of follicular growth occur during the nonluteal phase of the elephant estrous cycle. Each wave is associated with an increase in estrogen production that stimulates an LH surge. Thus, in contrast to serum analyses, urinary estrogen monitoring appears to be a reliable method for characterizing follicular activity in the elephant. Zoo Biol 22:443–454, 2003. © 2003 Wiley‐Liss, Inc.     

Suppressive effect of dynorphin-(1–13) on luteinizing hormone release in conscious castrated rats

The effect of intraventricular administration of dynorphin-(1–13) of luteinizing hormone (LH) release was studied in castrated conscious rats. The administration of 5 μg of dynorphin-(1–13) into the lateral ventricle inhibited LH secretion. Intravenous administration of naloxone blocked this suppressive effect of dynorphin on LH release. These results suggest a possible role of dynorphin, in addition to β-endorphin and Met⁵-enkephalin, in the control of LH release in male rats.     

Luteinizing hormone response to injection of synthetic gonadotrophin releasing hormone or infusion of oestradiol-17 beta in heifers

The effects of intracarotid injection of synthetic gonadotrophin releasing hormone (GnRH) as well as of intracarotid oestradiol infusion, on plasma luteinizing hormone (LH) levels in heifers were examined. The LH response in five ovariectomized heifers after administration of 100 μg of GnRH was biphasic, and more abrupt than in the cycling animals or in heifers with reproductive disorders. The first LH peak in ovariectomized heifers appeared 2 min after injection (fast response), and the second one about 15–30 min later (slow response). In all other heifers the fast response was never observed, and the mean estimated LH secretion was much lower. The LH response to intracarotid infusion of 3 μg of oestradiol-17β observed in ovariectomized heifers was also biphasic, although the first peak of LH was observed 4 h after the infusion had been terminated.     

Restoration of the periovulatory follicle-stimulating hormone surges in sera by luteinizing hormone releasing hormone in phenobarbital-blocked rats.

The periovulatory increases of follicle-stimulating hormone (FSH) in rat sera can be divided into two phases. The first phase consists of a rise and fall during proestrus and the second phase consists of a rise and fall during estrus. The second phase was not blocked by phenobarbital (100 mg/kg BW) injected i.p. between the first and second phases. In contrast, phenobarbital administered prior to the onset of the first phase blocked both phases of increased serum FSH. In phenobarbital-blocked rats, administration of luteinizing hormone releasing hormone (LHRH) during proestrus, either by s.c. injection (10 μg) or by a 3 hr constant-rate i.v. infusion (50 ng/hr), simulated both the proestrous and estrous phases of increased serum FSH. These results indicate that 1) the second phase of the serum FSH rise is itself not susceptible to phenobarbital blockade, 2) a proestrous mechanism susceptible to phenobarbital alteration is necessary for both phases of increased serum FSH to occur, and 3) administration of LHRH to phenobarbital-blocked rats during proestrus restores both phases of FSH release.     

Effect of follicle-stimulating hormone and luteinizing hormone during bovine in vitro maturation on development following in vitro fertilization and nuclear transfer

The effects of luteinizing hormone (LH) (0, 100, 10,000 lU/ml) and follicle-stimulating hormone (FSH) (20 μg/ml) supplementation during in vitro maturation of slaughterhouse-derived oocytes on polar body formation and embryo development subsequent to in vitro fertilization and nuclear transfer were evaluated. Go-nadotropin supplementation of maturation medium in the presence of serum neither enhanced the proportion of oocytes forming a polar body nor significantly affected development following in vitro fertilization or nuclear transfer, except at the highest LH concentration. A very high concentration of LH (10,000 lU/ml) significantly decreased polar body formation, initial cleavage, and blastocyst development (P < 0.05). © 1993 Wiley-Liss, Inc.     

Autocrine role of estrogens in the augmentation of luteinizing hormone receptor formation in cultured rat granulosa cells

The effects of estrogens on gonadotropin-stimulated luteinizing hormone (LH) receptor formation were examined in primary cultures of rat granulosa cells. Granulosa cells were cultured for 3 days with increasing concentrations of follicle-stimulating hormone (FSH) in the presence or absence of native and synthetic estrogens. Follicle-stimulating hormone stimulated LH receptor formation in a dose-dependent fashion, and estrogens enhanced the FSH-stimulated LH receptor content by decreasing the apparent ED50 of FSH. At 6.25 ng/ml FSH, the enhancement in LH receptor was estrogen dose dependent, with an ED50 value of about 3 X 10(-9) M for 17 beta-estradiol. The increased LH receptor content seen in cells treated with FSH and estrogen was correlated with increased cAMP production by these cells in response to LH stimulation. Time course studies revealed enhancement of FSH-stimulated LH receptor induction at 48 and 72 h of culture. Granulosa cells were also cultured with FSH for 2 days to induce functional LH receptors, then further cultured for 3 days with LH in the presence or absence of estrogens. At 30 ng/ml LH, increasing concentrations of estrogens maintained LH receptor content in a dose-dependent fashion, with their relative estrogenic potencies in keeping with reported binding affinities to estrogen receptors. An autocrine role of estrogens on LH receptor formation was further tested in granulosa cells treated with FSH and an aromatase substrate (androstenedione) to increase estrogen biosynthesis. Cotreatment with semipurified estrogen antibodies partially blocked the FSH stimulation of LH receptors, whereas nonimmune serum was ineffective. Also, inclusion of diethylstilbestrol prevented the inhibitory effect of the estrogen antibodies. Thus, local estrogens in ovarian follicles may play an autocrine role in granulosa cells to enhance LH receptor formation and to increase granulosa cell responsiveness to the LH surge, with subsequent ovulation and adequate corpus luteum formation.     

Effects of active immunization against gonadotropin releasing hormone on serum luteinizing hormone,progesterone levels and estrous cycles in the guinea pig

Mature female guinea pigs that had been observed to undergo three consecutive periods of estrus at approximately 16-day intervals were immunized with either 100 μg gonadotropin releasing hormone (GnRH) conjugated to 100 μg bovine serum albumin (BSA) or 100 μg BSA alone during diestrus (day 5–10) of the fourth cycle. Booster immunizations were administered 32 days after the first injection. Animals were bled by cardiac puncture at the time of first injection and at 16, 32, 48 and 64 days. Animals were necropsied at 64 days after first treatment.Daily observation indicated that vaginal manifestation of estrus was not apparent after a period equal to one estrous cycle in seven of ten GnRH immunized guinea pigs and after two cycles in the remaining three GnRH immunized guinea pigs. Estrous cycles persisted in BSA treated females throughout the experiment.Serum luteinizing hormone (LH) declined significantly by 32 days after the first immunization against GnRH and remained lower than both pretreatment values and levels in control animals at the same bleeding times throughout the experiment. Serum progesterone levels were significantly lower in the GnRH immunized group than in the control group at 48 and 64 days.At necropsy the weight of the ovaries of GnRH immunized guinea pigs was significantly lower than that of controls. Corpora lutea and antral follicles were present in both GnRH treated and control females. The presence of serum progesterone levels and of antral follicles in the GnRH immunized females suggests that a low level of gonadotropic support may have persisted to 64 days after initiation of treatment.Results indicate that immunization against GnRH can reduce LH and progesterone levels and induce cessation of estrous cycles in the guinea pig.     

The role of protein synthesis in the stimulation by LH of prostaglandin accumulation in rat preovulatory follicles

Preovulatory follicles isolated from immature rats, treated with pregnant mare's serum gonadotropin, were incubated and the accumulation of prostaglandin E measured. The addition of luteinizing hormone (5 μg/ml) increased this accumulation, after a lag period of 3 hours. This delay suggested the involvement of macromolecular synthesis in the mechanism of prostaglandin stimulation by luteinizing hormone. When the synthesis of protein was inhibited by the addition of puromycin (100 μM), the luteinizing hormone stimulation of prostaglandin E in these follicles was completely abolished. This inhibition was not seen with an analogue of puromycin, which does not inhibit protein synthesis, puromycin amino-nucleoside. These data suggest that concomitant protein synthesis is required for the luteinizing hormone stimulation of prostaglandin accumulation in rat follicles.     

Effect of a calcium channel blocker on the hypophyseal secretion of luteinizing hormone in intact and castrated rats of both sexes

The effect of verapamil on luteinizing hormone secretion by pituitary body was studied in normal and castrated male and female rats. Intragastric verapamil administration at a dose of 10 mg/g body weight two hours prior to decapitation decreased luteinizing hormone serum and pituitary levels in female rats only in proestrus. It is suggested that preovulatory luteinizing hormone secretion depends partially on estradiol-stimulated calcium transport.     

Suppression of gonadotropin secretion and prevention of ovulation in the rat by antiserum to synthetic gonadotropin-releasing hormone

Administration of an antiserum (0.10–0.25 ml/rat) to the synthetic decapeptide “luteinizing hormone releasing hormone” (LH-RH) suppressed the cyclic surge of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in proestrous rats and prevented ovulation; exogenous LH reversed the block of ovulation. Serum prolactin levels remained unaffected. In ovariectomized rats, the antiserum suppressed the elevated serum levels of both gonadotropins. These findings are compatible with the view that the synthetic decapeptide is identical with the natural hypothalamic hormone that regulates the secretion of both LH and FSH.     

Steroid-independent effect of gonadotropins on prostaglandin synthesis in rat Graafian follicles in vitro

The content of prostaglandins of the E-group (PGE) or F-group (PGF) was determined by radioimmunoassay in rat ovaries and in homogenates of cultured Graafian follicles. Intraperitoneal administration of luteinizing hormone (NIH-LH-S18; 10 μg/rat) at 9.00 h on any day of the estrous cycle caused an increase in ovarian PGE content within 5 h. The response was greatest on the day of proestrus (940% rise), i.e. when the ovary contains large follicles, and least at metestrus (80%). Follicles explanted from proestrous rats before the preovulatory gonadotropin surge responded to addition of LH (1–5 μg/ml) to the culture medium with a 10 to 30-fold increase in PGE and a 5-fold increase in PGF accumulation over a 5-h-period. Follicle stimulating hormone (NIH-FSH-S9; 10 μg/ml) caused a similar rise in follicular PGE accumulation, even after treatment of the FSH preparation with excess of an antiserum to the β-subunit of LH. Stimulation of follicular PG accumulation was unimpaired during suppression of progesterone and estrogen synthesis by aminoglutethimide. It is concluded that these steroids play no part in the mediation of the LH-effect on follicular prostaglandin formation.     

Plasma Luteinizing Hormone Response to Increasing doses of Synthetic Gonadotrophin-Releasing Hormone in Heifers

The dosenresponse relationship for a synthetic gonadotrophin-releasing hormone (GnRH) was studied in normally cycling heifers using the area under the luteinizing hormone (LH) curve as a response parameter. Oestrus was synchronized by an injection of 0.5 mg cloprostenol before the experiment started and after the 3rd treatment with GnRH. Treatment with GnRH as assigned in a Latin square included 5 dose levels (0, 10, 50, 100, 250 μg) and 5 treatment days over a period of 22 days. GnRH was capable of inducing an increase of plasma LH within 30 min after injection. Plasma LH response increased with increasing doses of GnRH, the largest increase being observed when the dose was raised from 50 μg to 100 μg. One heifer did not respond to any of the doses applied. The existence of an individual treshold dose of GnRH is suggested.     

Research for the effect of octylphenol on spermatogenesis and proteomic analysis in octylphenol-treated mice testes

OP (octylphenol), an environmental oestrogen was administered, and differentially expressed proteins were analysed in mice testes to clarify its mechanism of action in male sterility. Male Kunming suckling mice (10 days old) were subcutaneously injected with OP at a dose of 10 μg/kg per day, 50 μg/kg per day and 100 μg/kg per day as low-, medium- and high-dose groups, respectively, for 35 days. Animals in the control group received subcutaneous injections of olive oil at a dose of 10 μl/mouse per day. Serum oestradiol, testosterone, FSH (follicle stimulating hormone) and LH (luteinizing hormone) levels were measured on day 45. The left testes were removed for tissue analysis, and the right testes were analysed for differentially expressed proteins by using two-dimensional gel electrophoresis and MS. Tissue analysis showed that mice spermatogenesis was blocked at the round spermatid stage in the high-dose group, whereas no such changes were found in the medium- and low-dose groups. Higher serum oestradiol (P<0.05) and lower testosterone (P<0.05) levels were found in the medium- and high-dose groups. There was no significant difference in serum oestradiol and testosterone levels in the low-dose and control groups. No significant influence of OP was seen on serum FSH and LH levels in all OP-treated animals. The results from four differentially expressed proteins such as PPIA (peptidyl-prolyl cis-trans isomerase A), PEBP1 (phosphatidylethanolamine-binding protein1), TPI (triose-phosphate isomerase) and TCP-1 (T-complex protein 1) in the high-dose and control groups showed up-regulation of PPIA expression and down-regulation in PEBP1, TPI and TCP-1 expressions. These findings will contribute to clarify the mechanism of male sterility by environmental oestrogens.     

Effect of estrogens on β-hydroxy-β-methylglutaryl coenzyme a reductase activity and cholesterol levels

The effect of estrogens on hepatic β-hydroxy-β-methylglutaryl coenzyme A reductase activity and cholesterol in serum and liver of ovarietcomized rats on normal diet, 2% cholestyramine diet or 2% cholesterol diet was investigated. Estrogen administration to ovariectomized rats on normal diet resulted in increased reductase activity and was correlated with decreased serum cholesterol and increased liver cholesterol levels wlth mestranol (ME), ethinyl estradiol (EE) and estradiol benzoate (EB, 250 μg) but increased serum and liver cholesterol levels with 25 μg and 100 μg EB administration. The increased stimulation of reductase activity by estrogen administration was absolished when rats were fed a 2% cholesterol diet. Cholestyramine feeding markedly increased reductase activity in livers of ovariectomized rats. These studies show that estrogens are not absolutely required for the stimulation of reductase activity and therefore is consistent with the model in which cholesterol functions as a feedback repressor of reductase activity.