T.A. Parkening

Plasma and pituitary concentrations of LH, FSH, and Prolactin in aging C57BL/6 mice at various times of the estrous cycle ☆

Plasma and pituitary concentrations of LH, FSH, and prolactin (Prl) were measured by RIA in 2-4, 7-8, 12-13 and 16-20 month-old female C57BL/6 mice during various stages of the estrous cycle. In general, gonadotropin concentrations tended to rise with increasing age and Prl concentrations tended to decline. Pronounced differences existed, however, between the four age groups around the time of the LH surge. LH secretion declined progressively with increasing age at 21.00 hr of proestrus. Aged mice, 16-20 months old, had significantly lower plasma concentrations of LH than did other age groups. It is not known whether age-related changes in the ovary, pituitary, or hypothalamus are largely responsible for differences in the secretion of LH, FSH and Prl in aging C57BL/6 mice.

Lithium: Short-term and chronic effects on plasma testosterone and luteinizing hormone concentrations in mice

The effects of short-term and chronic lithium administration on the concentrations of plasma testosterone (T) and luteinizing hormone (LH) were evaluated in C57BL/6 mice, maintained on a fixed photoperiod of LD 14:10 (white lights on at 06:00 h, CST). Lithium chloride was injected intraperitoneally twice daily (at 09:00 and 16:00 h) in groups of adult male mice at a dosage of 2.5 meq/kg for 7 days, and 1.25 meg/kg for 21 days. Circulating levels of T and LH were measured by standard radioimmunoassay (RIA) methods. Plasma T levels showed a significant increase in mice treated with lithium for 7 days as compared to those in saline-injected control animals. However, there was no significant difference in the concentrations of plasma T between chronic (21 days) lithium-treated mice and the matched control. Plasma LH levels remained unchanged following both short-term and chronic lithium treatment.

Neuroendocrine Function in Transgenic Male Mice with Human Growth Hormone Expression

The neuroendocrine effects of human growth hormone (hGH) secretion were studied in adult male mice into which an hGH gene fused with mouse metallothionein 1 (mMT-1) promoter had been introduced. Intact transgenic mice had significantly greater plasma luteinizing hormone (LH) levels than did normal littermate controls. Castration increased LH levels in normal mice but was without effect on plasma LH levels in the transgenic mice. In vitro LH secretion and pituitary LH content were higher in the intact transgenic mice than in intact controls, while there was no significant difference in pituitary LH levels and in vitro LH secretion between the 2 groups of castrate animals. Intact transgenic mice exhibited a greater median eminence (ME) norepinephrine (NE) turnover than control animals, but ME NE turnover did not increase after castration in the transgenic animals as was the case in control mice. Castrate mice expressing the hGH gene had plasma levels of prolactin (PRL) similar to those seen in castrate controls, which was unexpected based on a previous study showing greatly attenuated PRL levels in intact hGH mice when compared to intact controls from the same line. Dopamine (DA) turnover in the ME was not significantly affected by the presence of the hGH gene, suggesting that the difference in plasma PRL levels between normal and transgenic mice is mediated through changes in PRL-regulating factors other than DA. In conclusion, the expression of the mMT-1/hGH hybrid gene in male mice leads to major alterations in LH secretion and lesser changes in PRL secretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Lithium-induced changes in the plasma and pituitary levels of luteinizing hormone, follicle stimulating hormone and prolactin in rats

Adult male Sprague-Dawley rats, maintained under a controlled photoperiod of LD 14:10 (white lights on at 06:00 h, CST), were injected with lithium chloride and changes in the levels of plasma and pituitary homogenates of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin (PRL) were examined to evaluate the effects of this anti-manic drug on reproductive function. Two groups of rats were injected with lithium chloride intraperitoneally, twice daily at 09:00 and 16:00 h, for 2 and 7 days at a dosage of 2.5 meq/Kg body weight. Plasma and pituitary levels of LH, FSH and PRL were measured by radioimmunoassay. Plasma levels of LH were significantly (P less than 0.05) increased after 2 days of lithium treatment. In contrast, a significant (P less than 0.005) reduction in plasma levels of LH was evident when lithium injections were continued for 7 days. The plasma levels of FSH remained unaffected by lithium treatment by either time period. Lithium administered for 2 days did not bring about any significant alteration in the plasma levels of PRL, although there was a significant (P less than 0.002) reduction in plasma PRL levels after 7 days treatment. The concentrations of pituitary LH, FSH and PRL remained unchanged after 2 and 7 days of lithium treatment.

Effects of Aging on the Activity of Hypothalamic Dopamine-Beta-Hydroxylase during Various Stages of the Estrous Cycle in C57BL/6 Mice

Hypothalamic dopamine-β-hydroxylase (DBH) activity and plasma luteinizing hormone (LH) concentrations were analyzed in female C57BL/6 mice aged 2–4, 7–8, 12–13, and 16–20 months at various times of th

Plasma and pituitary concentrations of luteinizing hormone, follicle-stimulating hormone and prolactin in aged, ovariectomized CD-1 and C57BL/6 mice

Plasma and pituitary concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and prolactin (Prl) were determined by radioimmunoassay in young (2-4 months-old) and aged CD-1 (14-18 months-old) and C57BL/6 (16-22 months-old) mice one month after ovariectomy. In young, ovariectomized mice, plasma and pituitary concentrations of LH and FSH were significantly higher, whereas concentrations of Prl were significantly lower than those in control mice (sham-operated). In contrast, plasma concentrations of LH, FSH and Prl were not statistically different in aged, ovariectomized mice and aged, control mice. There were also no differences in pituitary concentrations of the three hormones when comparing the same aged C57BL/6 mice, although the aged, ovariectomized CD-1 mice exhibited higher pituitary levels of each hormone than those of their controls. The pituitary of the aged mouse responds differently to ovariectomy than that of the young mouse because of age-related changes in the ovary and/or hypothalamic-hypophyseal complex.

Acute lithium treatment suppresses the proestrous LH surge in mice: chronic lithium leads to constant diestrus

Although the therapeutic usefulness of lithium in manic-depressive psychosis is now well-established, a number of basic and clinical studies in recent years have shown that the administration of this anti-manic drug produces a wide range of adverse endocrine and metabolic effects. The present study was undertaken in order to examine (a) what effects acute lithium administration might have on the preovulatory surge of luteinizing hormone (LH) during proestrus, and (b) whether chronic lithium administration has any adverse effect on the estrous cycle in C57BL/6 mice. Acute injections of lithium on the day of proestrus (at 10.00, 16.00 and 18.00 h; LD 14:10; lights on at 05.00 h CST) at a dosage of 5 mEq/kg b. wt. led to a significant (P less than 0.01) suppression of the LH surge that normally occurs in the evening of proestrus at 21.00 h. Chronic administration of lithium, on the other hand, resulted in a complete disruption in the regularity of the estrous cycle. This was characterized by an increasing number of mice showing a continuous diestrous vaginal smear during the first week of exposure to lithium, after which all of the lithium-treated mice completely stopped cycling and entered into constant diestrus. These results represent for the first time that lithium has significant adverse effects on the reproductive function in the female, especially in regard to the proestrous LH surge and estrous cyclicity in mice. Since these adverse effects were manifested under conditions when plasma lithium concentrations were within or around the therapeutic range, our results provide important conceptual information concerning possible adverse effects of lithium on the reproductive function in the human female.

Melatonin's inhibition of pituitary, adrenal, testicular and accessory gland growth in male Golden Hamsters: Pineal dependence and organ differences with shielding and intracranial surgery

Testes, accessory glands, pituitaries and adrenal glands from 101 male Golden Hamsters (55–65 days old) were weighed after 4 weeks of daily injections of vehicle or 25μg or 2500μg of melatonin, and 32–33 days after surgery. The surgical groups within each injection group were: (1) nonoperated (NO), (2) sham-pinealectomized (S), (3) sham-pinealectomized with black plastic shielding of the pineal region (S+Pl), (4) pinealectomized (PX), and (5) pinealectomized with black plastic shielding of the pineal region (PX+Pl). All injections were made between L11 and L11.75 in a fixed LD 14∶10 daily photoperiod. Absolute and relative organ weights were significantly depressed by 25 but not 2500μg melatonin. This effect of low dose melatonin was blocked by pinealectomy (PX, PX+Pl) in all four organ groups, but was blocked as well by the sham-operation (S, S+Pl) only in the case of the adrenal glands. Effects and organ weights in S animals were not modified in the S+Pl animals. But in vehicle-injected groups the S+Pl animals had significantly lower accessory organ weights in comparison with those of NO and S groups. These results aid in the further definition of the mechanisms of melatonins physiological actions as a chemical mediator within neuroendocrine timing controls, and show that the mechanisms for melatonins actions can differ in relation to eventual endpoint target tissue or organ studied.

Plasma and pituitary concentrations of LH, FSH and prolactin after injection of GnRH in aged female C57BL/6 mice

Plasma and pituitary concentrations of LH, FSH and prolactin (Prl) were compared by radioimmunoassay (RIA) in young mature (2-4 month-old) and aged (16-22 month-old) female C57BL/6 mice, following various experiments with IP injections of GnRH. Unanesthetized mice were bled by cardiac puncture either (1) at various time intervals following a single injection of 25 ng GnRH, (2) after several injections of 25 ng GnRH, or (3) after receiving excessively large doses of GnRH. From the RIA of plasma and pituitary concentrations of LH, it appeared that the pituitaries of aged mice were, in general, capable of responding to GnRH treatment, only to a lesser degree than that of the younger females. The exception was that the pituitaries of aged mice that were subjected to unusually high doses of GnRH continued to secrete higher levels of LH, whereas the response of the pituitaries in younger mice plateaued after receiving 25 ng GnRH. Plasma and pituitary concentrations of FSH and Prl remained fairly constant when aged GnRH-treated females were compared with aged controls. This was also true when FSH and Prl concentrations in the younger mice were compared with their controls, except for significantly higher plasma FSH and significantly lower pituitary FSH following several injections of GnRH. When the hormonal concentrations of the young and aged groups were compared in the various experiments, the older mice consistently exhibited higher levels of gonadotropin and lower levels of prolactin than those of the younger mice. In a separate experiment, in which a radioreceptor assay (RRA) was used to quantitate plasma LH in GnRH-treated mice, both age groups were found to have lower concentrations of LH (p less than 0.05) than those obtained by RIA from the same animals. The RRA to RIA ratio, however, was 0.84 for 2-4 month-old and 0.57 for 16-22 month-old mice. These studies suggest that the anterior pituitary of the aged mouse is less sensitive to GnRH stimulation.

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 radioimmunoassay 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.