Changes in plasma concentrations of LH, FSH and prolactin in ewes receiving melatonin and short-photoperiod treatments to induce early onset of breeding activity

Breeding activity was similarly advanced in ewes given continuous (s.c. implant) or timed (oral dose at 15.30 h) melatonin treatments or subjected to a short (8 h light: 16 h darkness) artificial photoperiod. Treatments commenced in mid-June and were terminated in mid-November. Weekly and serial blood samples were collected before and after treatments commenced, to ascertain the effects on plasma prolactin, LH and FSH concentrations. In addition, serial blood samples were collected for 24 h plasma prolactin and melatonin estimations before and after cessation of the treatments. Plasma prolactin levels were significantly reduced immediately following the start of the melatonin (implant and oral) and short-photoperiod treatments but 'rebounded' to levels greater than control values. The normal seasonal (spring) rise in plasma prolactin was noted in the following year. Before the onset of breeding activity, mean plasma LH and FSH concentrations and LH pulse frequency did not change following any of the treatments. The 24-h plasma melatonin profile accurately reflected the various applied treatments but had re-entrained to the prevailing (natural) photoperiod 1 week after termination of the treatments. There were no significant group differences in 24-h plasma prolactin levels 1 week before or 1 and 11 weeks after the treatments had ceased. Such treatments, although successfully advancing the onset of breeding activity and modifying the seasonal plasma prolactin rhythm, were not manifested through any apparent change in peripheral LH or FSH.     

Plasma and pituitary concentrations of LH, FSH and prolactin in aging mongolian gerbils

Samples of plasma and pituitary homogenates collected from female Mongolian gerbils (3–4, 11–13 and 20–25 month-old) at various stages of the estrous cycle were analyzed by radio-immunoassay for luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin (Prl). Plasma and pituitary LH concentrations were similar in all three age groups. Plasma FSH concentrations tended to increase with age while plasma Prl concentrations remained unchanged. Pituitary concentrations of FSH and Prl were variable between the age groups depending upon the stage of the estrous cycle. The inability of older gerbils to produce young appears to result primarily from age-related changes occurring in the uterus rather than from alterations in the hypothalamic-hypophyseal complex.     

Effects of morphine and naloxone on plasma levels of LH, FSH, prolactin and growth hormone in the immature male pig

The effects of acute i.v. administration of gonadotrophin-releasing hormone (GnRH; 0.1 micrograms/kg), morphine (3 mg/kg) and/or naloxone (0.5 mg/kg) on LH and FSH secretion was evaluated in young male pigs (approximately 6 weeks old) with venous brachiocephalic cannulae. The effects of morphine and/or naloxone treatments on prolactin and GH were also evaluated. The influence of morphine on hypophysial hormone secretion was also examined 2 days after castration. Animals treated with morphine and/or naloxone were compared with saline-injected control animals. Injection of GnRH induced 400 and 50% increases in LH and FSH respectively. Morphine and/or naloxone did not influence LH secretion in intact or castrated animals. Morphine suppressed (P less than 0.01) FSH levels 40-60 min after injection whereas naloxone had no effect. Castration eliminated morphine-induced suppression of FSH. Injection of morphine followed by naloxone resulted in acutely raised (P less than 0.05) FSH concentrations. Morphine induced a threefold increase (P less than 0.01) in prolactin within 30 min of injection and naloxone inhibited the effect of morphine. Levels of GH were increased (P less than 0.01) 20 min after morphine treatment and this increase was delayed when naloxone was given immediately after morphine. Naloxone alone did not affect prolactin or GH secretion. Castration caused increases in LH (P less than 0.05) and FSH (P less than 0.01), did not influence prolactin or GH, and reduced plasma testosterone to undetectable (less than 1.0 nmol/l) levels. These results suggest that in young male pigs the hypothalamic-hypophysial axis is responsive to GnRH and gonadal negative feedback.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of a two-hour early awakening and of bright light exposure on plasma patterns of cortisol, melatonin, prolactin and testosterone in man.

Bright light is a synchronizing agent that entrains human circadian rhythms and modifies various endocrine and neuroendocrine functions. The aim of the present study was to determine whether and how the exposure to a bright light stimulus during the 2 h following a 2 h earlier awakening could modify the disturbance induced by the the sleep deprivation on the plasma patterns of hormones whose secretion is sensitive to light and/or sleep, namely melatonin, prolactin, cortisol and testosterone. Six healthy and synchronized (lights on: 07.00-23.00) male students (22.5 +/- 1.1 years) with normal psychological profiles volunteered for the study in winter. The protocol consisted of a baseline control night (customary sleep schedule) followed by three shortened nights with a rising at 05.00 and a 2 h exposure to either dim light (50 lux; one week) or bright light (2000 lux; other week). Our study showed a phase advance of the circadian rhythm of plasma cortisol without significant modifications of the hormone mean or peak concentration. Plasma melatonin concentration decreased following bright light exposure, whereas no obvious modifications of plasma testosterone or prolactin patterns could be observed in this protocol.     

健康婴儿LH、FSH、雌二醇与睾酮的血清浓度

目的研究正常婴儿血LH、FSH、雌二醇(E2)与睾酮(T)的血清浓度变化。方法用免疫化学发光分析法对358名正常婴儿(男婴183,女婴175)的LH、FSH、E2和T水平进行测定,同时对3个月内婴儿的其他可能相关指标(出生体重、孕期、胎次、母亲年龄及分娩方式)进行了研究。结果(1)婴儿期4种激素水平变化男婴LH、FSH在2~3月龄时达高峰(LH3.5IU/L,FSH3.4IU/L),6月龄后趋平坦(LH1.5IU/L,FSH<1.5IU/L),T在2~4月龄时达高峰(9.15mmol/L)后快速下降,6月龄后稳定在一个较低的水平(<1.34nmol/L);女婴FSH在2~3月龄达高峰(7.1IU/L),LH与T在整个婴儿期的水平几乎是条直线(LH<4.7IU/L,T<2.49nmol/L)。男女婴的E2水平在生后快速下降,3月龄后达最低值。(2)性别差异LH和T在6月龄前男婴明显高于女婴,6月龄后无性别差异。FSH水平各月龄组女婴均高于男婴,E2除2月龄前女婴高于男婴外,3~12月龄时无性别差异。(3)3月龄内婴儿促性腺激素、性激素水平与出生体重、孕期、胎次、母亲年龄及分娩方式未显示相关关系。结论婴儿在2~4月龄时的血促性腺激素与性激素水平有个暂时的高峰期,并有明显性别差异,可能与两性性腺发育的不同调控机制有关。     

LH, FSH and progesterone level in the blood plasma of women with normal menstrual cycle]

Luteinizing hormone (LH), folliculostimulating hormone (FSH) and progesterone were studied by the radioimmunoassay in a group of 10 women throughout a normal menstrual cycle. The LH and the FSH peak occurs at the middle of the cycle. At the early follicular phase the FSH level was higher than that of the LH. During the follicular and the lutein phases the plasma progesterone level was 0.65 +/- 0.12 ng/ml and 12.4 +/- 2.3 ng/ml, respectively. The laboratory criteria of the normal ovular cycle are: a) a mid-cycle LH peak; b) plasma progesterone level at the lutein phase were 10-15 times greater than at the follicular one; c) progesterone peak at the mid-lutein phase; d) the duration of the lutein phase of 12-15 days.     

The menopausal transition: analysis of LH, FSH, estradiol, and progesterone concentrations during menstrual cycles of older women.

Studies of menstrual cycle length in large populations demonstrated that there is a striking increase in the variability of intermenstrual intervals just before menopause. The changes in serum concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), estradiol (E2), and progesterone (P) during menstrual cycles in a group of perimenopausal women were compared with the findings in young normal women. In 8 women, 46-56 years old with regular cycles, cycle length was shorter and the mean E2 concentration was lower than in younger women. There was a striking increase in FSH concentration throughout the cycle while LH remained in the normal range. In 2 women, 14 cycles of variable length were studied during 2 years of the menopausal transition. In some instances, hormonal changes associated with follicular maturation and corpus luteum function occurred in the presence of high, menopausal levels of LH and FSH with a diminished secretion of E2 and P. In others vaginal bleeding occurred during a fall in serum E2 with no associated rise in P. Cycles of variable length during the menopausal transition may be due either to irregular maturation of residual follicles with diminished responsiveness to gonadotropin stimulation, or to anovulatory vaginal bleeding that may follow estrogen withdrawal without evidence of corpus luteum function. The observation of elevated FSH concentrations and normal LH levels in perimenopausal women emphasizes the complexity of the hypothalamic-pituitary-ovarian regulatory system and suggests that LH and FSH are modulated independently at the level of the pituitary.     

FSH, LH and prolactin levels, ovarian follicular development and ovarian responsiveness to FSH in the Snell dwarf mouse

The homozygous Snell dwarf mouse is sterile. It has been shown that pituitary hormone levels are low in 3 month old animals except for FSH and LH whose pituitary contents and plasma concentrations are normal. In this study, the pituitary FSH, LH and prolactin (Prl) content, the FSH plasma concentration and the ovarian follicular development of the Snell dwarf mouse were studied at 18, 20, 24, 40 and 80 days of age. Normal mice were also studied at the same age and served as controls. Pituitary FSH was significantly lower in dwarf mice compared with controls during the period days 18 to 30, while plasma FSH was significantly lower during the period days 20 to 80. Pituitary LH was significantly lower in dwarf mice during the period days 18 to 40. In normal mice, pituitary Prl increased with age, but remained consistently low in dwarf mice. The normal number of growing follicles was similar in dwarf mice and controls up to day 30, but thereafter the total number of growing follicles was greater in the controls. In the dwarf mice, the production of antral follicles was low and there were no ovulations. The rates of atresia were similar in the two genotypes. The responsiveness of the dwarf mouse ovary to FSH was then examined. When dwarf and control mice were supplemented with FSH for 5 days starting at 24 days of age, the ovarian and uterine weights increase 6- and 5-fold, respectively, in the dwarf mice, and 2- to 3-fold in the normal mice.(ABSTRACT TRUNCATED AT 250 WORDS)     

Serum concentrations of LH and FSH in the healthy newborn

OBJECTIVE: A sex difference in fetal and neonatal pituitary-gonadal function has been well documented. The aim of the following study was to determine sex differences and patterns of basal LH/FSH in the neonatal period. DESIGN: Peripheral venous blood was obtained from 164 healthy full term newborns (91 males, 73 females) for clinically indicated laboratory examinations. RESULTS: In male newborns, LH values were initially low (days 1-5), increased between days 6 and 10, and reached maximum levels between days 16 and 20. Levels of FSH were initially low (days 1-5), increased between days 6 and 10 and reached maximum levels between days 11 and 15. In female newborns, LH levels were generally lower than in newborn boys; levels were initially low, then increased between days 11 and 15 and reached maximum levels at the end of the newborn period. FSH values were generally higher than in newborn boys; there were initially low values with a first peak between days 11 and 15 and a second peak between days 21 and 28. CONCLUSIONS: LH values in male newborns were higher and exceeded values in female newborns, whereas FSH values in female newborns exceeded male newborn values. Male newborns do not exhibit any peaks of LH and FSH activity, whereas female newborns exhibit two FSH peaks during this period.     

Effects of altered photoperiod or maternal melatonin administration on plasma prolactin concentrations in fetal lambs

During winter (December to March), when late-pregnant ewes were maintained under an artificial long-day photoperiod (16 h light) for 3 weeks or more before insertion of fetal vascular cannulae between 118 and 120 days of gestation (full term, 147 days), plasma prolactin concentrations in their fetal lambs were significantly increased throughout the last 3 weeks of gestation in comparison with values in similar aged fetuses from ewes experiencing only the natural short-day (less than 9 h light) winter photoperiod. When additional lighting was given only after vascular cannulation, fetal plasma prolactin increased steadily from low values, characteristic of winter pregnancies, to high values, characteristic of long-day (16 h light:8 h darkness) pregnancies. Maternal plasma prolactin concentrations changed in a similar way. During summer pregnancies (greater than 16 h light), plasma prolactin in fetal lambs was significantly reduced within 48 h when ewes were given melatonin by i.v. infusion for 14 h each night to simulate the winter duration of the nocturnal increase in plasma melatonin. Maternal plasma prolactin concentrations also decreased significantly when melatonin was given for 3 weeks, but not in a shorter experiment. Increases in fetal plasma prolactin were proportional to the basal prolactin concentration in fetuses injected i.v. with TRH or a dopaminergic antagonist, metoclopramide, to assess how photoperiod influenced the responsiveness of prolactin secretion to acute stimulation. The results confirm that photoperiod, rather than developmental maturity, is the principal determinant of plasma prolactin in the fetal lamb during the last third of gestation, and provide evidence that photoperiodic information is transmitted to the fetus through the diurnal rhythm of melatonin in the ewe.     

Modulation of prolactin receptors in cultured rat granulosa cells by FSH,LH and GnRH

The hormonal modulation of prolactin (PRL)-binding capacity of rat granulosa cells was studied. Granulosa cells obtained from immature, hypophysectomized, estrogen-treated rats were cultured for 2 days in a serum-free medium in the presence of various hormones. FSH treatment in vitro stimulated granulosa cell PRL-binding capacity by ~ 4–6-fold in a dose-dependent manner. Concomitant treatment with 10^?8 M GnRH inhibited the FSH-induced increase in PRL-binding capacity by 64%. In contrast, the inhibitory effect of GnRH was blocked by concomitant treatment with 10^?6 M of a GnRH antagonist, [D-pGlu¹, D-Phe², D-Trp^3,6]GnRH. PRL-binding capacity was also increased (~2-fold) by in vitro treatment with cholera toxin (10 μg/ml). In granulosa cells pre-treated with FSH in vitro for 2 days, hCG treatment for 2 additional days stimulated PRL-binding capacity in a dose-dependent manner (~ 2-fold). Likewise, treatment with LH (100 ng/ml) also stimulated PRL-binding capacity by ~ 2-fold. These in vitro studies demonstrated that gonadotropins (FSH, LH and hCG) directly enhanced PRL binding by granulosa cells, whereas GnRH inhibited FSH action.     

Effects of antiserum to thyrotrophin-releasing hormone on the concentrations of plasma prolactin, thyrotrophin and LH in the pro-oestrous rat

The possible role of thyrotrophin-releasing hormone (TRH) in causing the pro-oestrous surge of prolactin was investigated in conscious female rats by passive immunization with a specific anti-TRH serum raised in sheep. Blood samples were withdrawn through a previously implanted intra-atrial cannula. The i.p. injection of 1 ml anti-TRH serum, but not non-immune sheep serum, at 13.00 h of pro-oestrus delayed by about 1 h the onset of the prolactin surge, but the peak of the surge was similar to that in animals injected with the non-immune serum. The plasma concentrations of TSH were significantly reduced by the anti-TRH serum, but plasma concentrations of LH were not significantly affected. These results show that TRH may play an important role in the timing and initiation, but not the maintenance of the prolactin surge in the pro-oestrous rat.