Levels of LH-releasing hormone in hypophysial stalk plasma during an oestrogen-stimulated surge of LH in ovariectomized rats

1987 ◽  
Vol 112 (3) ◽  
pp. 351-359 ◽  
Author(s):  
W. J. de Greef ◽  
J. de Koning ◽  
A. M. I. Tijssen ◽  
B. Karels
Keyword(s):  
Jugular Vein ◽  
Ovariectomized Rats ◽  
In Vitro Bioassay ◽  
Portal Vessel ◽  
Oestradiol Benzoate ◽  
Portal Plasma ◽  
Endogenous Release ◽  
Lh Releasing Hormone ◽  
Hypophysial Portal

ABSTRACT Treatment of ovariectomized rats with 50 μg oestradiol benzoate, followed by 20 μg oestradiol benzoate 3 days later, induced surges of LH and FSH on the day following the second injection with oestradiol benzoate. During this surge of gonadotrophins, which was not blocked by the anaesthetic required to collect hypophysial stalk blood, increased hypophysial stalk plasma levels of immunoreactive LHRH were noted. Furthermore, the levels of LHRH in hypophysial portal blood were found to fluctuate. Measurement of LHRH in a pool of portal plasma revealed similar results when determined by radioimmunoassay and by a sensitive in-vitro bioassay. To mimic the observed release of LHRH during the surge of gonadotrophins, LHRH was infused, either systemically or directly into a long portal vessel, into oestrogen-treated, ovariectomized rats which had their endogenous release of LHRH blocked by pentobarbitone. An infusion of LHRH into the jugular vein, resulting in peripheral levels of LHRH which were somewhat lower than those measured in hypophysial stalk plasma, caused a surge of FSH similar to that found in rats used for collection of hypophysial stalk blood. When compared with the values in the latter animals, however, the levels of LH became two to four times higher by this infusion of LHRH. When LHRH was infused directly into a long portal vessel to mimic the observed secretion rate of LHRH during the oestrogen-stimulated surge of gonadotrophins, then the surges of LH and FSH were lower than those observed in the rats used for collection of stalk blood. J. Endocr. (1987) 112, 351–359

PROGESTERONE TREATMENT INCREASES PITUITARY OESTRADIOL RETENTION IN THE OVARIECTOMIZED NORMAL FEMALE RAT BUT NOT IN THE MALE NOR IN THE ANDROGEN- OR OESTROGEN-STERILIZED FEMALE RAT

1977 ◽  
Vol 84 (2) ◽  
pp. 268-280 ◽  
Author(s):  
Robert D. Lisk ◽  
Lawrence A. Reuter
Keyword(s):  
Testosterone Propionate ◽  
Ovariectomized Rats ◽  
Normal Female ◽  
Nuclear Fraction ◽  
Female Rat ◽  
Treatment Conditions ◽  
Oestradiol Benzoate ◽  
Pre Treatment

ABSTRACT Pituitary retention of [3H]oestradiol in ovariectomized rats was measured following in vivo progesterone pre-treatment and found to be significantly increased after 48, 72, 96 and 120 h of pre-treatment. Increased [3H]oestradiol retention was also observed for at least up to 72 h after removal of the progesterone pre-treatment source. This retention was measured as dpm per mg dry tissue weight. [3H]Oestradiol retention was also measured in the nuclear fraction of tissues incubated with [3H]oestradiol in vitro. Following 72 h of in vivo progesterone pre-treatment, the nuclear fraction from the pituitary was found to retain significantly more [3H]oestradiol than corresponding fractions from non-treated animals. In contrast to ovariectomized females, no increase in [3H]oestradiol retention was found in the pituitary of orchidectomized males pre-treated with progesterone for 72 h. [3H]Oestradiol retention by pituitaries of ovariectomized rats injected on the day of birth with 200 μg oestradiol benzoate (OeB) or 500 μg testosterone propionate (TP) was significantly decreased in comparison to control animals. When the rats were pre-treated in vivo with oestradiol for 6 or 72 h and [3H]oestradiol retention was measured 6 or 24 h after this pre-treatment, the OeB and TP treated animals retained significantly less [3H]oestradiol under most treatment conditions. Progesterone pretreatment for 24 or 72 h in vivo followed by measurement of [3H]oestradiol retention immediately or 6 or 24 h later resulted in a significant increase in [3H]oestradiol retention for the control animals. In contrast, the neonatally OeB or TP treated animals differed significantly by not showing increased retention. When [3H]oestradiol retention of the pituitary was measured in vitro following homogenization at 0°C and incubation at 37°C for 1 h, the nuclear fraction from both OeB and TP treated animals was found to retain less hormone per unit DNA; however, this decrease was significant only for the TP animals. Thus, males and androgen- or oestrogensterilized females have an altered and reduced augmentation of pituitary oestradiol retention in response to both oestrogen and progesterone pretreatments.

GONADOTROPHIN RELEASE IN VITRO, IN THE PRESENCE AND ABSENCE OF LUTEINIZING HORMONE RELEASING HORMONE, BY PITUITARY GLANDS FROM OVARIECTOMIZED AND SHAM-OPERATED IMMATURE FEMALE RATS OF VARIOUS AGES

1981 ◽  
Vol 88 (3) ◽  
pp. 375-379
Author(s):  
J. DULLAART
Keyword(s):  
Female Rats ◽  
Ovariectomized Rats ◽  
Immature Female ◽  
Releasing Hormone ◽  
Incubation Experiments ◽  
Immature Rats ◽  
Pituitary Glands ◽  
Lh Releasing Hormone

Hemipituitary glands of immature female rats, aged 10, 15, 20, 25, 30 and 35 days and either ovariectomized or sham-operated 5 days earlier, were incubated for 2 h in vitro with or without LH releasing hormone. Concentrations of LH and FSH were determined at the end of the incubations in the incubation media and in the hemipituitary glands, and also in the sera collected at the beginning of the incubation experiments. Results showed that in many instances gonadotrophin release was higher after incubation of glands of ovariectomized rats than with glands of control animals. However, these effects of ovariectomy were much smaller than those observed in vivo and were generally absent in rats of less than 20 days of age. It was concluded that ovariectomy may change the secretory characteristics of the gonadotrophic cells of immature rats but that such changes were largely restricted to immature rats older than 20 days.

Release of LH in vitro from anterior pituitary glands of ovariectomized rats by LRH or elevated potassium concentration after pre-treatment with oestradiol benzoate in vivo

1982 ◽  
Vol 99 (2) ◽  
pp. 206-210 ◽  
Author(s):  
A. M. I. Tijssen ◽  
J. de Koning ◽  
G. P. van Rees
Keyword(s):  
Ovariectomized Rats ◽  
Bicarbonate Buffer ◽  
High K ◽  
Oestradiol Benzoate ◽  
Negative Effect ◽  
Pituitary Glands ◽  
Lh Release ◽  
Pre Treatment ◽  
Positive Effect

Abstract. Pituitary glands from ovariectomized rats which had been pre-treated with oestradiol benzoate (OeB) or solvent oil were incubated in Krebs-Ringer bicarbonate buffer with glucose containing either LRH (1000 ng/ml) or a high K+ concentration (50 mM). OeB (7 μg sc) or oil was injected at 2.5 or 6.5 h before the beginning of the incubation experiment or during the three preceding days (three daily injections). Depending upon the period during which the pituitary glands had been exposed to OeB LH release induced by LRH was inhibited (negative effect of OeB) or augmented (positive effect). When the glands were incubated in medium containing high K+, only the negative effect of OeB pre-treatment was seen. It is concluded that that part of LRH-induced LH release which is mimicked by high K+ is involved in the negative effect of OeB, but not in its positive effect.

INFLUENCE OF OESTROGEN ADMINISTRATION IN VIVO AND IN VITRO ON THE RELEASE AND SYNTHESIS OF PROLACTIN FROM INCUBATED PITUITARIES

1977 ◽  
Vol 86 (4) ◽  
pp. 714-721 ◽  
Author(s):  
Marta E. Apfelbaum ◽  
S. Taleisnik
Keyword(s):  
Incubation Medium ◽  
Direct Action ◽  
Ovariectomized Rats ◽  
Spontaneous Release ◽  
Prolactin Cells ◽  
Oestradiol Benzoate ◽  
Pre Treatment ◽  
Higher Doses

ABSTRACT The release and synthesis of prolactin were studied in incubated adenohypophyses from ovariectomized rats. After a 4 h incubation period the prolactin concentration in the medium markedly increased whereas that in the gland was reduced. However, the concentration of prolactin in the system, tissue plus medium, after 4 h was almost twice as much as that present at the beginning of incubation indicating spontaneous synthesis. This spontaneous release and synthesis of prolactin was greatly increased in incubated glands from ovariectomized oestrogen-treated rats. Oestradiol benzoate was injected in doses of 2.5, 5.0 or 10.0 μg/rat 2 or 24 h before killing the animals. Lower effects were obtained in glands from 2 h-oestradiol-pre-treated rats than from 24 h-oestradiol-primed rats. Oestradiol-17β (55, 166, 500 and 1500 ng/ml) added to the incubation medium also enhanced the release and synthesis of prolactin and the effect was more marked in glands from oestrogen injected rats than in those of non-treated animals. The increase was dose-related although the higher doses were less effective. These results provide further evidence of the effect of oestrogen on the release and synthesis of prolactin by a direct action on the pituitary gland. They also show that oestradiol pre-treatment in vivo increase the response of the prolactin cells towards oestradiol in vitro.

Levels of dopamine and thyrotrophin-releasing hormone in hypophysial stalk blood during an oestrogen-stimulated surge of prolactin in the ovariectomized rat

1985 ◽  
Vol 105 (1) ◽  
pp. 107-112 ◽  
Author(s):  
W. J. de Greef ◽  
W. Klootwijk ◽  
B. Karels ◽  
T. J. Visser
Keyword(s):  
High Performance ◽  
Vascular System ◽  
Ovariectomized Rats ◽  
Thyrotrophin Releasing Hormone ◽  
Releasing Hormone ◽  
Methanolic Extracts ◽  
Oestradiol Benzoate ◽  
Hypothalamic Dopamine ◽  
Reliable Increase ◽  
Hypophysial Portal

ABSTRACT The changes in hypothalamic release of dopamine and thyrotrophin-releasing hormone (TRH) into the hypophysial portal vascular system during an oestrogen-stimulated surge of prolactin in ovariectomized rats were investigated. A single injection of 5 μg oestradiol benzoate resulted in a reliable increase in the plasma levels of prolactin during the afternoon 3 days later. Anaesthesia did not block this afternoon surge of prolactin, although its magnitude was only half of that of unanaesthetized rats. Before and during this surge, hypophysial stalk blood was collected into methanol to analyse the hypothalamic release of dopamine and TRH. Immunoreactive TRH in these methanolic extracts eluted as a single peak with the same retention time as authentic TRH on reverse-phase high performance liquid chromatography. In comparison to the morning values, levels of dopamine decreased and those of TRH increased in hypophysial stalk blood by 50 and 240% respectively. These data indicate that hypothalamic dopamine and TRH may be involved in the afternoon surge of prolactin. Daily treatment with parachlorophenylalanine, an inhibitor of serotonin synthesis, reduced the hypothalamic release of TRH by 50%, but did not prevent the afternoon surge of prolactin and TRH induced by oestradiol benzoate. J. Endocr. (1985) 105, 107–112

Plasma gonadotrophin concentrations, pituitary gonadotrophin content and pituitary responsiveness to LHRH in rats treated with LHRH and oestradiol benzoate

1987 ◽  
Vol 115 (3) ◽  
pp. 469-475 ◽  
Author(s):  
G. A. Schuiling ◽  
N. Pols-Valkhof ◽  
H. Moes ◽  
T. R. Koiter
Keyword(s):  
Plasma Concentration ◽  
Plasma Concentrations ◽  
Ovariectomized Rats ◽  
Prolonged Treatment ◽  
High Dose ◽  
Response Curves ◽  
Simultaneous Treatment ◽  
Control Value ◽  
Oestradiol Benzoate

ABSTRACT Suppression of gonadotrophin secretion during prolonged treatment with a high dose of LHRH was studied. Long-term ovariectomized rats were infused for 6 days with various doses of LHRH (25, 50, 100, 250 or 500 ng/h) with or without simultaneous treatment with oestradiol benzoate (OB; 3 μg/s.c. injection); a further group was treated with OB only. The effects of these treatments were studied on plasma concentrations of LH and FSH, the pituitary content of LH and FSH and on LH and FSH secretion in vitro (perifusion) in the unstimulated state and following maximal LHRH stimulation (1 μg LHRH/ml perifusion medium). Administration of LHRH caused a dose-dependent reduction in plasma concentrations of LH and FSH and depleted the pituitary LH/FSH stores. Treatment with OB lowered the plasma concentration of LH to about 30% and that of FSH to about 65% of the control values. Administration of OB plus a low dose of LHRH (25 or 50 ng/h) markedly stimulated the secretion of LH but not of FSH, so that the plasma concentrations of LH were fully restored to the control value. With higher rates of LHRH infusion, OB caused no enhancement of the plasma concentrations of LH and FSH. The experiments in vitro revealed a sensitizing, i.e. stimulatory effect, of OB on LHRH-stimulated LH and FSH secretion. However, the higher the rate of infusion of LHRH the smaller the sensitizing effect. Interpolation from dose–response curves showed that an LHRH infusion rate of about 150 ng/h (which would establish a plasma concentration of LHRH of about 68 pmol/l) would have no effect. With still higher rates of infusion of LHRH, the effect of OB was either inhibitory (LH) or absent (FSH). The present experiments show that, depending on dose and length of treatment, both LHRH and OB can have variable effects on the secretion of LH and FSH: LHRH, while depleting and desensitizing the pituitary gland, stimulates the release of LH, whilst OB, which is known to suppress the secretion of LHRH by the hypothalamus, augments the rates of unstimulated and LHRH-stimulated LH and FSH secretion. The augmenting effect of OB on the latter component of LH and FSH secretion can be suppressed with high doses of LHRH. However, these experiments also show that even with doses as high as 500 ng LHRH/h, infused continuously for 6 days, plasma concentrations of LH and FSH are not reduced by more than 60–70%. J. Endocr. (1987) 115, 469–475

Hypothalamic-pituitary function in neonatally oestrogen-treated male rats

1992 ◽  
Vol 134 (2) ◽  
pp. 279-NP ◽  
Author(s):  
L. Pinilla ◽  
P. Garnelo ◽  
F. Gaytan ◽  
E. Aguilar
Keyword(s):  
Olive Oil ◽  
Plasma Concentrations ◽  
Male Rats ◽  
Lhrh Agonist ◽  
Gonadotrophin Secretion ◽  
Oestradiol Benzoate ◽  
Lh Releasing Hormone ◽  
Wistar Male Rats

ABSTRACT Neonatal oestrogen administration to male rats permanently impaired the function of the pituitary-testicular axis possibly by inhibiting neonatal gonadotrophin secretion. To analyse the hypothalamus and/or pituitary involvement in this inhibition, pituitary responsiveness to acute stimulation with LH-releasing hormone (LHRH) was studied in vivo and in vitro in Wistar male rats injected on day 1 of age with oestradiol benzoate (OB) or olive oil. FSH and LH pituitary content and plasma concentrations were reduced in oestrogenized male rats at days 10 and 16 of age. Likewise, the in-vivo increase in gonadotrophin plasma concentrations after acute stimulation with LHRH was almost completely suppressed in 10-and 16-day-old oestrogenized males. In vitro, the increased secretion of FSH after LHRH stimulation was abolished and the LH response strongly reduced in pituitaries from oestrogenized males. Finally, the effects of neonatal oestrogenization were not abolished by treatment from day 1 to day 15 with an LHRH agonist (0·01 μg/kg per 12 h). We conclude that in male rats the effects of oestrogenization are due to both a reduction in LHRH endogenous secretion and a decrease in the pituitary responsiveness to LHRH. Journal of Endocrinology (1992) 134, 279–286

A SENSITIVE IN VITRO BIOASSAY METHOD FOR LUTEINIZING HORMONE (LH) ACTIVITY

1973 ◽  
Vol 74 (4) ◽  
pp. 642-658 ◽  
Author(s):  
M.-P. Van Damme ◽  
D. M. Robertson ◽  
P. Romaní ◽  
E. Diczfalusy
Keyword(s):  
Luteinizing Hormone ◽  
Incubation Medium ◽  
Antagonistic Effect ◽  
Dose Effect ◽  
In Vitro Bioassay ◽  
Experimental Conditions ◽  
Bioassay Method ◽  
The Mean ◽  
Lh Releasing Hormone

ABSTRACT A specific and sensitive in vitro bioassay method is described for the measurement of LH activity of HCG, HMG and human hypophyseal gonadotrophin (HHG) preparations. The method is based on the principle that a linear relationship exists between graded doses of HCG, HMG or HHG preparations and the amount of testosterone released into the incubation medium by decapsulated mouse testes. The sensitivity of the method is 0.4 mIU/ml incubation medium for HCG and 2 mIU/ml for HMG. The useful range of the method is 0.4– mIU/ml for HCG and 2–32 mIU/ml for HMG preparations. A 3 + 3 point design with 6 individual observations per dose is used. Under these experimental conditions the mean index of precision (γ) in 44 assays was 0.22. All HCG, HMG and HHG preparations yielded parallel dose-effect lines. In the concentrations studied, the assay was not influenced by the presence of FSH, ACTH, STH, LTH, vasopressin, oxytocin and LH releasing hormone activities. The high LH contamination of the highly purified TSH preparations studied precluded an adequate assessment of a possible synergistic or antagonistic effect of TSH on the assay.

ASSESSMENT OF GH RELEASING HORMONE ACTIVITY IN SEPHADEX-SEPARATED FRACTIONS OF PORCINE HYPOTHALAMIC EXTRACTS BY HYPOPHYSEAL PORTAL VESSEL INFUSION IN THE RAT

1975 ◽  
Vol 78 (3) ◽  
pp. 428-434 ◽  
Author(s):  
Jiro Takahara ◽  
Akira Arimura ◽  
Andrew V. Schally
Keyword(s):  
Growth Hormone ◽  
Growth Hormone Releasing Hormone ◽  
Hormone Activity ◽  
Prolactin Release ◽  
Releasing Hormone ◽  
Portal Vessel ◽  
Lh Rh ◽  
Lh Releasing Hormone

ABSTRACT Growth hormone-releasing hormone (GH-RH) activity in Sephadex G-25 fractions of porcine stalk median eminence (SME) extracts was examined in vivo by infusing these samples into a rat hypophyseal portal vessel. The increment of immunoreactive GH levels in the serum was used as the index for GH-RH activity. The GH-RH activities were found in two different locations: in the early fractions Nos. 3–4, and in somewhat retarded fraction No. 7. These GH-RH activities were not due to TRH, vasopressin, or potassium. The location of LH releasing hormone (LH-RH) and prolactin release-inhibiting hormone (PR-IH) determined in this in vivo system was in agreement with those found in other in vivo and in vitro assay systems for LH-RH and PR-IH, respectively. These results help validate this assay system.

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