EFFECT OF SYNTHETIC THYROTROPHIN RELEASING FACTOR ON PROLACTIN AND LUTEINIZING HORMONE SECRETION IN MALE AND FEMALE RATS DURING VARIOUS REPRODUCTIVE STATES

1975 ◽  
Vol 67 (3) ◽  
pp. 425-430 ◽  
Author(s):  
R. P. DEIS ◽  
NIA ALONSO
Keyword(s):  
Hormone Secretion ◽  
Female Rats ◽  
Male Rats ◽  
Serum Prolactin ◽  
Serum Prolactin Level ◽  
Luteinizing Hormone Secretion ◽  
Male And Female Rats ◽  
Serum Lh ◽  
The Mean ◽  
Lh Secretion

SUMMARY The effect of synthetic thyrotrophin releasing factor (TRF) on serum prolactin and LH concentrations was determined by radioimmunoassay in male, cyclic and pseudopregnant female rats. A solution of TRF (0·1, 0·25, 0·5 and 1 μg/rat) was injected i.v. at 17.00 h into rats pretreated with sodium pentobarbitone at 13.00 h. A group of male rats was also treated with TRF at 11.00 h after pretreatment with sodium pentobarbitone at 07.00 h. Fifteen minutes after TRF administration, blood samples were obtained by heart puncture. Doses of 0·25, 0·5 and 1 μg TRF significantly increased the serum prolactin concentration in pro-oestrous rats. The mean serum prolactin level after the injection of 0·5 and 1 μg into oestrous rats and 0·5 μg TRF into dioestrous day 2 rats, was significantly greater than the control values. Injection of TRF on day 1 of dioestrus had no effect. Serum LH concentration was not significantly modified by the various doses of TRF administered. On day 3 of pseudopregnancy a significant increase of serum prolactin values was obtained with 0·5 and 1 μg TRF. On day 7 of pseudopregnancy a dose of 0·5 μg produced the same effect, but on day 10 of pseudopregnancy only 1 μg TRF significantly increased serum prolactin levels when compared with the control rats. In male rats serum prolactin concentration was significantly greater than the control values after TRF treatment either in the morning or the afternoon. The response was similar to that obtained in pro-oestrous rats. The results suggest that the ability of synthetic TRF to stimulate prolactin release exists in both female and male rats and that TRF does not affect LH secretion.

EFFECTS OF NALOXONE ON LUTEINIZING HORMONE AND PROLACTIN IN SERUM OF RATS

1980 ◽  
Vol 85 (2) ◽  
pp. 307-315 ◽  
Author(s):  
M. S. BLANK ◽  
A. E. PANERAI ◽  
H. G. FRIESEN
Keyword(s):  
Female Rats ◽  
Male Rats ◽  
Ovariectomized Rats ◽  
Serum Prolactin ◽  
Immature Female ◽  
Subcutaneous Injections ◽  
Serum Lh ◽  
Opiate Peptides ◽  
Lh Release ◽  
Lh Secretion

The effects of subcutaneous injections of the opiate antagonist naloxone on the tonic and phasic secretion of prolactin and LH were studied in rats. During development, resting levels of prolactin in serum were decreased by naloxone (2·5 mg/kg body wt) on days 24,45 and 50 in female rats and on days 28,45 and 50 in male rats. In the adult, naloxone (2·5 mg/kg body wt) decreased basal levels of serum prolactin in male rats and levels during oestrus in female rats. In 25-day-old female rats, serum LH rose from resting levels within 7·5 min of naloxone administration (2·5 mg/kg body wt) and returned to pretreatment levels by 30 min, while prolactin fell by 7·5 min and remained low for as long as 60 min after treatment. Furthermore, a tenfold lower dose of naloxone (0·25 mg/kg body wt) did not raise basal levels of serum LH but still decreased resting levels of serum prolactin in immature female rats (24 days old). The effect of naloxone (2·5 mg/kg body wt) on phasic LH release was studied in 29-day-old immature female rats primed on day 27 with pregnant mare serum gonadotrophin (PMSG). In these PMSG-treated rats the onset of the prolactin surge was blunted by naloxone while it had no effect on phasic LH release. Naloxone (5 mg/kg body wt) also induced a rise in levels of serum LH in ovariectomized rats and, if administered with morphine, it reversed the short-term inhibition of LH secretion caused by morphine. However, naloxone was ineffective after pretreatment with oestradiol benzoate. These findings suggest that the responses of serum LH and prolactin to naloxone were dissociated and that oestrogens and opiate peptides may have interacted to regulate secretion of LH.

Episodic secretion of luteinizing hormone and androgen in male rats

1983 ◽  
Vol 97 (1) ◽  
pp. 145-153 ◽  
Author(s):  
P. Södersten ◽  
P. Eneroth ◽  
A. Pettersson
Keyword(s):  
Hormone Secretion ◽  
Male Rats ◽  
Intact Male ◽  
Serum Lh ◽  
Light Darkness ◽  
The Mean ◽  
Androgen Secretion ◽  
Lh Secretion ◽  
Androgen Levels ◽  
Intact Rats

Sequential blood samples were obtained at hourly intervals from intact male rats during various phases of the light: darkness cycle. Measurement of the serum concentrations of LH and androgen showed that both hormones were secreted episodically, with a secretory episode defined as an increment and subsequent decrement in the serum hormone level exceeding the analytical intra-assay imprecision. Episodes of androgen secretion varied greatly in amplitude (from 1·04 to 30·90 nmol/l) in individual males, occurred during any phase of the light: darkness cycle and were preceded by one or two episodes of LH secretion. Individual males could show more than one episode of androgen secretion during an 18-h sampling period (mean ± s.e.m. = 1·7 ± 0·7 pulses/10 h). Mean values of serum LH and androgen in groups of animals obscured the episodic pattern of hormone secretion shown by individual animals. Castration reduced serum androgen to non-detectable levels within 2 h and produced a temporary decline in serum LH levels and abolition of the episodic pattern of LH secretion. These effects were prevented by testosterone treatment at the time of castration. There was a gradual increase in serum LH levels and in the amplitude of the LH secretory episodes for 1 week after castration. Treatment of castrated rats with testosterone-filled constant-release implants (10 or 20 mm long) produced high and stable serum androgen levels and episodes of LH secretion of low amplitude 1 week after castration. A constant concentration of serum androgen comparable to the mean level of intact rats, produced by implantation of 5 mm long testosterone implants 3 weeks earlier, resulted in a pattern of episodic LH secretion which was similar to that of intact rats. Subcutaneous injection of various doses of testosterone (5, 15 or 45 μg) in castrated rats produced a dose-dependent increase in serum androgen levels within 30 min of injection and thereafter the levels declined. Injection of 15 μg testosterone produced a pulse-like increase in serum androgen concentrations with an amplitude within the range of that observed in intact rats. Injection of this amount of testosterone in castrated rats in which serum LH levels had been suppressed by prior implantation of 20 mm long testosterone implants produced no change in serum LH levels. It is suggested that androgen primarily modifies the amplitude of the LH secretory episodes and that episodic fluctuations in serum androgen levels have no immediate effect on the pattern of LH secretion. Constant serum androgen levels comparable to the mean level of intact rats are sufficient for maintenance of the normal episodic pattern of LH secretion.

Effects of galanin-like peptide on luteinizing hormone secretion in the rat: sexually dimorphic responses and enhanced sensitivity at male puberty

2006 ◽  
Vol 291 (6) ◽  
pp. E1281-E1289 ◽  
Author(s):  
J. M. Castellano ◽  
V. M. Navarro ◽  
R. Fernández-Fernández ◽  
J. Roa ◽  
E. Vigo ◽  
...  
Keyword(s):  
Luteinizing Hormone ◽  
Hormone Secretion ◽  
Metabolic Stress ◽  
Female Rats ◽  
Metabolic Status ◽  
Male Rats ◽  
Intracerebral Injection ◽  
Luteinizing Hormone Secretion ◽  
Male Puberty ◽  
Lh Secretion

Reproductive function is exquisitely sensitive to adequacy of nutrition and fuel reserves, through mechanisms that are yet to be completely elucidated. Galanin-like peptide (GALP) has recently emerged as another neuropeptide link that couples reproduction and metabolism. However, although the effects of GALP on luteinizing hormone (LH) secretion have been studied, no systematic investigation on how these responses might differ along sexual maturation and between sexes has been reported. Moreover, the influence of metabolic status and potential interplay with other relevant neurotransmitters controlling LH secretion remain ill defined. These facets of GALP physiology were addressed herein. Intracerebral injection of GALP to male rats induced a dose-dependent increase in serum LH levels, the magnitude of which was significantly greater in pubertal than in adult males. In contrast, negligible LH responses to GALP were detected in pubertal or adult female rats at diestrus. Neonatal androgen treatment to females failed to “masculinize” the pattern of LH response to GALP. In addition, metabolic stress by short-term fasting did not prevent but rather amplified LH responses to GALP in pubertal males, whereas these responses were abrogated by pharmacological inhibition of nitric oxide synthesis. We conclude that the ability of GALP to evoke LH secretion is sexually differentiated, with maximal responses at male puberty, a phenomenon which was not reverted by manipulation of sex steroid milieu during the critical neonatal period and was sensitive to metabolic stress. This state of LH hyperresponsiveness may prove relevant for the mechanisms relaying metabolic status to the reproductive axis in male puberty.

Changes in the characteristics of pulsatile luteinizing hormone secretion during the oestrous cycle and after ovariectomy and oestrogen treatment in female rats

1982 ◽  
Vol 94 (2) ◽  
pp. 177-182 ◽  
Author(s):  
Takashi Higuchi ◽  
Masazumi Kawakami
Keyword(s):  
Hormone Secretion ◽  
Pulse Amplitude ◽  
Pulse Frequency ◽  
Oestrous Cycle ◽  
Female Rats ◽  
Ovariectomized Rats ◽  
Luteinizing Hormone Secretion ◽  
Oestrogen Treatment ◽  
Serum Lh ◽  
Lh Release

Changes in the characteristics of LH secretory pulses in female rats were determined in different hormonal conditions; during the oestrous cycle and after ovariectomy and oestrogen treatment. The frequency and amplitude of the LH pulses were stable during the oestrous cycle except at oestrus when a pattern could not be discerned because of low LH concentrations. These were significantly lower than those measured during other stages of the cycle. Mean LH concentrations and LH pulse amplitudes increased with time up to 30 days after ovariectomy. The frequency of the LH pulse was unchanged 4 days after ovariectomy when mean LH levels had already increased. The frequency increased 10 days after ovariectomy and then remained stable in spite of a further increase in mean serum LH concentrations. Oestradiol-17β injected into ovariectomized rats caused a decrease in LH pulse amplitude but no change in pulse frequency. One day after treatment with oestradiol benzoate no LH pulse was detectable, probably because the amplitude was too small. A generator of pulsatile LH release is postulated and an oestrogen effect on its function is discussed.

Effects of valproate-induced alteration of the GABAergic system on pulsatile luteinizing hormone secretion in ovariectomized women

1996 ◽  
Vol 135 (3) ◽  
pp. 293-298 ◽  
Author(s):  
Joaquin Lado-Abeal ◽  
Jose L Liz ◽  
Carlos Rey ◽  
Manuel Febrero ◽  
Jose Cabezas-Cerrato
Keyword(s):  
Luteinizing Hormone ◽  
Sodium Valproate ◽  
Pulse Generator ◽  
Hormone Secretion ◽  
Gabaergic System ◽  
Luteinizing Hormone Secretion ◽  
Serum Lh ◽  
Nutrition Service ◽  
Significant Difference ◽  
Lh Secretion

Lado-Abeal J, Liz JL, Rey C, Febrero M, Cabezas-Cerrato J. Effects of valproate-induced alteration of the GABAergic system on pulsatile luteinizing hormone secretion in ovariectomized women. Eur J Endocrinol 1996;135:293–8. ISSN 0804–4643 It is well established that valproate increases hypothalamic concentrations of γ-aminobutyric acid (GABA). Although little research has been done on the role of GABA in the control of pulsatile luteinizing hormone (LH) secretion in humans, our group recently found that administration of valproate had no significant effect on pulsatile LH secretion in late follicular and mid-late luteal phase normal women. However, the results of several studies of rats suggest that GABAergic regulation of LH secretion may depend on steroid levels. The objective of this work was to determine whether regular administration of sodium valproate inhibits pulsatile LH secretion in ovariectomized women. Twelve women who had undergone ovariectomy for causes other than malignant tumors were each studied in two 8 h sessions, in each of which blood samples were taken every 5 min. The first session was the control; for the second, 400 mg of sodium valproate was administered every 8 h during the seven preceding days and at 08.00 h and 14.00 h on the day of the study session. Serum valproate was determined by repolarization fluorescence spectrophotometry, and LH, estradiol and progesterone by radioimmunoassay. The serum LH series were subjected to a deconvolution procedure to reconstruct the pattern of pituitary LH secretion. Luteinizing hormone pulses were identified by the authors' nonparametric method. Control and post-valproate results were compared with regard to number of pulses, pulse duration, the quantity of LH secreted in each pulse, interpulse interval and mean serum LH level. There was no statistically significant difference between control and post-valproate results for any of the variables considered. It is concluded that sustained serum valproate levels do not alter pulsatile secretion of LH in ovariectomized women. This implies that, in humans, GABA is probably not a decisive factor in the regulation of the GnRH pulse generator. J Cabezas-Cerrato, Endocrinology and Nutrition Service, General Hospital of Galicia, c/Galeras s/n 15705, Santiago de Compostela, La Coruña, Spain

scholarly journals Galanin Enhancement of Gonadotropin-Releasing Hormone-Stimulated Luteinizing Hormone Secretion in Female Rats Is Estrogen Dependent

Endocrinology ◽  
2003 ◽  
Vol 144 (2) ◽  
pp. 484-490 ◽  
Author(s):  
Cynthia L. Splett ◽  
Joseph R. Scheffen ◽  
Joshua A. Desotelle ◽  
Vicky Plamann ◽  
Angela C. Bauer-Dantoin
Keyword(s):  
Luteinizing Hormone ◽  
Hormone Secretion ◽  
Gonadotropin Releasing Hormone ◽  
Gonadal Steroids ◽  
Female Rats ◽  
Luteinizing Hormone Secretion ◽  
Ovx Rats ◽  
Lh Secretion ◽  
Lines Of Evidence

The hypothalamic peptide GnRH is the primary neuroendocrine signal regulating pituitary LH in females. The neuropeptide galanin is cosecreted with GnRH from hypothalamic neurons, and in vitro studies have demonstrated that galanin can act at the level of the pituitary to directly stimulate LH secretion and also augment GnRH-stimulated LH secretion. Several lines of evidence have suggested that the hypophysiotropic effects of galanin are important for the generation of preovulatory LH surges. To determine whether the pituitary actions of galanin are enhanced by the preovulatory steroidal milieu, LH responses to galanin administration (with or without GnRH) were examined in: 1) ovariectomized (OVX); 2) OVX, estrogen (E)-primed; and 3) OVX, E- and progesterone-treated female rats. Results from the study indicate that galanin enhances GnRH-stimulated LH secretion only in the presence of E (in OVX, E-primed, or E- and progesterone-treated rats). Galanin alone does not directly stimulate LH secretion under any of the steroid conditions examined. In the absence of gonadal steroids (OVX rats), galanin inhibits GnRH-stimulated LH secretion. These findings suggest that the primary pituitary effect of galanin is to modulate GnRH-stimulated LH secretion, and that the potentiating effects of galanin occur only in the presence of E.

Regulation of luteinizing hormone secretion in prepubertal male and female rats

Life Sciences ◽  
1982 ◽  
Vol 31 (20-21) ◽  
pp. 2167-2170 ◽  
Author(s):  
Rüdiger Schulz ◽  
Annemarie Wilhelm ◽  
Karl Martin Pirke ◽  
Albert Herz
Keyword(s):  
Luteinizing Hormone ◽  
Hormone Secretion ◽  
Female Rats ◽  
Luteinizing Hormone Secretion ◽  
Male And Female ◽  
Male And Female Rats

CIRCADIAN FLUCTUATIONS OF SERUM HORMONE LEVELS IN PREPUBERTAL MALE AND FEMALE RATS

1976 ◽  
Vol 83 (2) ◽  
pp. 269-279 ◽  
Author(s):  
K. D. Döhler ◽  
W. Wuttke
Keyword(s):  
Age Groups ◽  
Serum Testosterone ◽  
Female Rats ◽  
Serum Prolactin ◽  
Male And Female ◽  
Hormone Levels ◽  
Male And Female Rats ◽  
Serum Lh ◽  
Serum Hormone ◽  
Old Females

ABSTRACT Diurnal variations in serum hormone levels during 2 different stages of prepubertal development were investigated in male and female rats. Groups of 13 to 18 and 25 to 30 day old male and female rats were decapitated at 4-hour by intervals during a period of 24 h. Their blood was collected and hormones were measured by radio-immunoassay. FSH levels were constantly high in 13 to 18, but low in 25 to 30 day old females. FSH was low in younger males, and significantly higher but without diurnal fluctuations in the older males. Serum LH was low in approximately 40% of the 13 to 18 day old females, while 40% had moderately high levels, and the remaining females extremely high levels of the hormone. Most of the extremely high LH peaks were found at 15.00 h and some at 03.00 h. Older females and males of both age groups had constantly low serum LH levels. Serum oestradiol was high in males and females during days 13 to 18, but it was lower in the 25 to 30 day old animals. In the young females prolactin was slightly elevated between 15.00 h and 19.00 h, while in the males the serum prolactin fluctuations were not significant. Serum testosterone was low in females at all times. The 13 to 18 day old males had higher testosterone levels than the 25 to 30 day old males. Both groups showed slight, but insignificant fluctuations in serum testosterone. These results confirm result published previously and furthermore they demonstrate the existence of circasemedian or circadian rhythms for both the gonadotrophins and gonadal steroids. These results, also suggest that the maturation of the positive feedback action of oestradiol on gonadotrophin release in female rats occurs between day 10 and 20.

Serum cholesterol levels of inbred rats

1964 ◽  
Vol 207 (3) ◽  
pp. 631-633 ◽  
Author(s):  
David Kritchevsky ◽  
Shirley A. Tepper
Keyword(s):  
Body Weight ◽  
Serum Cholesterol ◽  
Inbred Strains ◽  
Female Rats ◽  
Male Rats ◽  
Liver Cholesterol ◽  
Cholesterol Levels ◽  
Male And Female Rats ◽  
Males And Females ◽  
The Mean

Changes in serum cholesterol levels with age have been studied in male and female rats of three inbred strains (BN, DA, and Lewis) and one random-bred strain (Wistar). The mean serum cholesterol levels at each age differed among strains. Serum cholesterol levels (mg/100 ml) for male rats at 30, 60, and 90 days were: BN-65, 46, and 47; DA-105, 85, and 101; Lewis-79, 76, and 57; and Wistar-64, 63, and 73. For female rats the values were: BN-56, 45, and 47; DA-86, 74, and 91; Lewis-77, 83, and 67; and Wistar-59, 71, and 83. The variation of serum cholesterol with age was different between strains, but similar for males and females within each strain. There was no correlation between body weight and serum cholesterol. Liver cholesterol levels (mg/100 g) determined at 90 days were, for the males, BN-187, DA-233, Lewis-247, and Wistar-300, and for the females, BN-188, DA-244, Lewis-216, and Wistar-249. No correlation with body weight or serum cholesterol was observed.

Hyperprolactinaemia attenuates the gonadotrophin releasing hormone receptor response to gonadectomy in rats

1982 ◽  
Vol 95 (2) ◽  
pp. 267-274 ◽  
Author(s):  
R. N. Clayton ◽  
L. C. Bailey
Keyword(s):  
Female Rats ◽  
Male Rats ◽  
Serum Prolactin ◽  
Intact Male ◽  
Adult Rats ◽  
Releasing Hormone ◽  
Receptor Response ◽  
Serum Lh ◽  
Gonadotrophin Releasing Hormone ◽  
Qualitative Index

Measurement of pituitary gonadotrophin releasing hormone (Gn-RH) receptor content provides a qualitative index of prior exposure of the pituitary gland to endogenous Gn-RH. The effect of moderate hyperprolactinaemia (serum prolactin = 95–250 μg/l), achieved with three pituitary grafts beneath the renal capsule, on the pituitary Gn-RH receptor content and serum LH responses to gonadectomy of adult rats has been studied. In males the presence of hyperprolactinaemia for 7 days completely prevented the increase in Gn-RH receptor content 3 days after castration and inhibited the serum LH rise by 45%. By 6 days after castration, Gn-RH receptors had increased in the hyperprolactinaemic castrated animals but values were 33% lower than in sham-grafted controls, while the serum LH increase was attenuated by 30%. Pituitary LH content was also lower in grafted castrated animals 6 days after castration. Hyperprolactinaemia for 3 weeks had no effect on Gn-RH receptors or pituitary LH content of intact male rats, although basal serum LH was decreased by 50%. Hyperprolactinaemia also attenuated the increases in Gn-RH receptors, serum LH and pituitary LH which occurred 6 days after ovariectomy in female rats. In all experiments the pituitary content of prolactin was reduced by 80–90% in animals bearing pituitary grafts. These results suggest that hyperprolactinaemia restricts the Gn-RH receptor response to gonadectomy by decreasing endogenous hypothalamic Gn-RH secretion.

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