ANTERIOR PITUITARY SENSITIVITY IN IMMATURE FEMALE RATS STIMULATED WITH GONADOTROPHIN RELEASING HORMONE IN VIVO: EFFECT OF PRIMING WITH OESTROGEN, PREGNANT MARE SERUM GONADOTROPHIN OR BRAIN LESION

1977 ◽  
Vol 74 (1) ◽  
pp. 99-109 ◽  
Author(s):  
D. DE ZIEGLER ◽  
M. WILKINSON ◽  
DANIELLE CASSARD ◽  
K. B. RUF
Keyword(s):  
Brain Lesion ◽  
Treated Group ◽  
Female Rats ◽  
Similar Degree ◽  
Female Rat ◽  
Immature Female ◽  
Releasing Hormone ◽  
Gonadotrophin Releasing Hormone ◽  
Pregnant Mare Serum Gonadotrophin

An investigation of pituitary sensitivity, assessed in terms of increments in plasma LH and FSH concentrations, to stimulation with one or two injections of gonadotrophin releasing hormone (GnRH) was carried out on 26-day-old immature female rats which had received one of the following priming treatments: 10 μg oestradiol benzoate (OB) as a single injection on day 23 or day 25, or on both days; 10 i.u. pregnant mare serum gonadotrophin (PMSG) on day 24; an electrochemical brain lesion placed in the mediobasal hypothalamus on day 23; control animals received either vehicle alone or a sham lesion. Pituitary sensitivity assessed at 10.00 h on day 26, after one or two injections of GnRH (100 ng/100 g body weight, s.c.), was enhanced to a similar degree in the three groups treated with OB in terms of LH (P < 0-01). The FSH response also increased after OB treatment but was not statistically significant. In contrast, 48 h after the injection of PMSG (i.e. when the rats were in a 'pro-oestrous-like' condition) pituitary sensitivity in terms of both LH and FSH dropped sharply (P < 0·001). In lesioned animals, pituitary sensitivity to one injection of GnRH was unchanged. A second GnRH injection administered after a 60 min interval induced a slightly larger LH response in control animals. In contrast, the ratio of the second response to the first increased in animals treated with PMSG, despite the state of overall decrease in sensitivity, being 4·5:1 in PMSG-treated rats versus 1·4:1 in controls. In a second set of experiments, we investigated the variation of pituitary sensitivity in conjunction with an experimentally induced gonadotrophin surge. In animals treated with OB on day 23 and with 1 mg progesterone at 12·00 h on day 26, pituitary sensitivity was increased at both 14.00 and 17.00 h as compared with that in the day 23 OB-treated group at 10.00 h. The PMSG-treated animals maintained their state of decreased responsiveness at 14.00 h, but exhibited increased pituitary sensitivity at the time of the gonadotrophin surge (17.00 h). These results show that OB increases pituitary sensitivity to GnRH in 26-day-old female rats and that the induction of a gonadotrophin surge further increases this sensitivity. In contrast, PMSG-treated rats displayed a state of decreased responsiveness 48 and 52 h, but not 55 h, after the injection. Pituitary sensitivity on the second day after PMSG treatment thus clearly differs from that observed during pro-oestrus in the adult cyclic female rat.

IN-VITRO STUDIES OF THE EFFECTS OF OESTROGEN PRETREATMENT ON THE SENSITIVITY OF THE IMMATURE FEMALE RAT PITUITARY GLAND TO STIMULATION WITH GONADOTROPHIN RELEASING HORMONE

1977 ◽  
Vol 74 (1) ◽  
pp. 11-21 ◽  
Author(s):  
M. WILKINSON ◽  
D. DE ZIEGLER ◽  
DANIELLE CASSARD ◽  
K. B. RUF
Keyword(s):  
Pituitary Gland ◽  
Brain Lesion ◽  
Culture Technique ◽  
Female Rats ◽  
Female Rat ◽  
Immature Female ◽  
Releasing Hormone ◽  
Gonadotrophin Releasing Hormone ◽  
Unilateral Brain Lesion

The effects of oestrogen priming on the sensitivity of the anterior pituitary gland to stimulation with gonadotrophin releasing hormone (GnRH) was investigated in immature female rats using a new organ culture technique. Hemipituitary glands obtained from animals primed with a single dose of oestradiol benzoate (OB; 20 μg/100 g body weight) released significantly more LH when pulsed with GnRH (4 nmol/l) than did control hemipituitary glands. This potentiating effect was detectable as early as 5 days after birth. After a second stimulation, LH secretion remained high. These results were compared with those obtained from animals treated to induce increased levels of endogenous oestrogen on day 26 of life. Thus, hemipituitary glands were obtained from animals given two injections of OB, an injection of pregnant mare serum gonadotrophin (PMSG) or a unilateral brain lesion placed in the basal hypothalamus. Pituitary tissue was stimulated as before with a pulse of GnRH. Two injections of OB enhanced the sensitivity to stimulation. Conversely, both PMSG and lesion treatment severely reduced the sensitivity to GnRH, although PMSG-treated and lesioned animals have been used as models for the study of ovulation.

Daily administration of gonadotrophin-releasing hormone increases pituitary gonadotroph number and pituitary gonadotrophin content, but not serum gonadotrophin levels, in female rats on day 1 of dioestrus

1992 ◽  
Vol 132 (3) ◽  
pp. 395-NP ◽  
Author(s):  
F. Kotsuji ◽  
K. Hosokawa ◽  
T. Tominaga
Keyword(s):  
Single Cells ◽  
Chronic Administration ◽  
Serum Levels ◽  
Female Rats ◽  
Female Rat ◽  
Dependent Manner ◽  
Releasing Hormone ◽  
Rat Pituitary ◽  
Gonadotrophin Releasing Hormone ◽  
Lh Cells

ABSTRACT Gonadotrophin-releasing hormone (GnRH) has been shown to regulate the synthesis and release of gonadotrophins acutely, yet few studies have investigated the chronic effects of this agent on pituitary gonadotrophins. In the present study we determined the effect of chronic administration of GnRH on the female rat pituitary gland. Rats of 8 weeks of age were injected s.c. with various doses of GnRH daily for 30 days. After completion of the GnRH treatment, treated rats and age-matched controls were killed by decapitation at 09.00 h on the first day of dioestrus, as determined from vaginal smears. Treatment with 10 ng–10 μg GnRH/day increased pituitary contents of FSH and LH in a dose-dependent manner. The change in FSH content was much greater than that of LH content. The pituitary FSH content of rats treated with 40 μg GnRH was significantly less than that of rats treated with 10 μg GnRH. There was a marked increase in the number of cells which stained positively for FSH (266%) and LH (28%) in the anterior pituitary of rats given 10 μg GnRH, but there was no demonstrable change in the areas of single cells stained positively for FSH and LH. Serum levels of LH, FSH and oestradiol were not affected by the GnRH treatment. These data indicate that chronic administration of GnRH is capable of increasing the pituitary gonadotrophin content and numbers of FSH and/or LH-stained cells and that FSH cells are affected more than LH cells by the GnRH treatment. The increase in pituitary gonadotrophin content, however, does not necessarily produce an increase in circulating levels of gonadotrophins. Journal of Endocrinology (1992) 132, 395–400

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.

In-vivo inhibition of the preovulatory LH surge by substance P and in-vitro modulation of gonadotrophin-releasing hormone-induced LH release by substance P, oestradiol and progesterone in the female rat

1991 ◽  
Vol 130 (2) ◽  
pp. 169-175 ◽  
Author(s):  
T. Battmann ◽  
S. Mélik Parsadaniantz ◽  
B. Jeanjean ◽  
B. Kerdelhué
Keyword(s):  
Substance P ◽  
Inhibitory Effect ◽  
Female Rat ◽  
Neuroendocrine Control ◽  
Lh Surge ◽  
Releasing Hormone ◽  
Lh Release ◽  
Gonadotrophin Releasing Hormone

ABSTRACT The effects of substance P (SP) on the preovulatory surge of LH and on the inhibitory and stimulatory effects of oestradiol-17β and progesterone on gonadotrophin-releasing hormone (GnRH)-induced LH release were investigated in vivo and in vitro in the rat. A single s.c. injection of 100 μg SP at 12.00 h on the day of pro-oestrus significantly decreased the preovulatory surge of LH. In vitro, the inhibitory effect of oestradiol-17β on GnRH-induced LH release was not modified by treatment with SP. The stimulatory effect of progesterone on GnRH-induced LH release was reduced by treatment with SP. It is concluded that SP may play a modulatory role in the neuroendocrine control of the preovulatory LH surge. Journal of Endocrinology (1991) 130, 169–175

Precocious ovulation induced by human chorionic gonadotrophin in the immature female rat: comparison of follicle growth induced by treatment with human chorionic gonadotrophin and by electrical stimulation of the hypothalamus

1985 ◽  
Vol 106 (1) ◽  
pp. 61-66 ◽  
Author(s):  
H. M. A. Meijs-Roelofs ◽  
P. Kramer ◽  
P. Osman
Keyword(s):  
Electrical Stimulation ◽  
Ovarian Follicle ◽  
Treated Group ◽  
Chorionic Gonadotrophin ◽  
Human Chorionic Gonadotrophin ◽  
Female Rats ◽  
Female Rat ◽  
Follicle Growth ◽  
Immature Female ◽  
Stimulation Of

ABSTRACT Precocious first ovulation, preceded by an endogenous preovulatory LH surge, could be predictably induced in immature female rats by administering repeated injections of human chorionic gonadotrophin (hCG). Administration of a dose of 0·05–0·075 i.u. hCG, four times a day from day 28 to day 31 of age resulted in a highly constant ovulatory response: at 4·0±0·0 days after the start of treatment 7·7±0·3 (n = 15) ova were found. Use of a higher dose of hCG (0·1 i.u.) resulted in lower numbers of ova (5·6±0·4, n = 7; P<0·005) whereas use of a lower dose of hCG (0·025–0·038 i.u.) resulted in a less constant timing of the induced ovulation at 5·4±0·2 days after the start of treatment (n = 7; P<0·0005). In animals treated with the dose of 0·05–0·075 i.u. hCG, a positive correlation was found between body weight at the start of treatment and the number of ova released (r = 0·75, n = 25; P<0·001). Ovarian follicle dynamics were studied on the various days of hCG treatment (dose 0·05–0·075 i.u.) and compared with the follicle changes that take place after electrical stimulation of the hypothalamus, performed on day 28, a treatment known to result in first ovulation 4–5 days later. In both groups a decrease in the number of the smallest and the middle-sized antral follicles as compared with their respective controls was seen, whereas numbers of follicles in the largest, 'ovulatable' size classes gradually increased. The pattern was more conspicuous in the hCG-treated group, presumably related to greater constancy in timing of the ovulatory response in this group. The present data support the view that endogenous changes in LH secretion during late prepuberty (which have been found to take place) play a significant role in stimulating late-prepubertal follicle growth and the ensuing first ovulation. J. Endocr. (1985) 106, 61–66

Testosterone maintains pituitary and serum FSH and spermatogenesis in gonadotrophin-releasing hormone antagonist-suppressed rats

1986 ◽  
Vol 108 (1) ◽  
pp. 101-107 ◽  
Author(s):  
M. A. Rea ◽  
G. R. Marshall ◽  
G. F. Weinbauer ◽  
E. Nieschlag
Keyword(s):  
Serum Testosterone ◽  
Treated Group ◽  
Male Rats ◽  
Testis Weight ◽  
Releasing Hormone ◽  
Serum Lh ◽  
Hypophysectomized Rats ◽  
Gonadotrophin Releasing Hormone ◽  
Vehicle Treated Control

ABSTRACT Groups of adult male rats were treated continuously for 30 days with either vehicle or the potent gonadotrophin-releasing hormone (GnRH) antagonist, (N-Ac-d-Nal(2)1,d-pCl-Phe2,d-Trp3,d-hArg (Et2)6,d-Ala10)-GnRH (RS 68439; 35 μg/day). In addition, groups of vehicle- and antagonist-treated rats received s.c. testosterone implants sufficient to maintain serum testosterone concentrations 3·5- to 5-fold higher than those of vehicle-treated control rats. After 30 days of antagonist treatment serum LH, FSH and testosterone concentrations were at or below the detection limits of their respective assays and pituitary FSH content and GnRH receptor binding were reduced, relative to control animals, by 77 and 98% respectively. Testis weight in antagonist-treated rats was reduced by 75% and spermatogenesis was suppressed to an extent comparable to that observed in hypophysectomized rats. Testosterone, which caused a 40% reduction in serum FSH relative to control animals, prevented the antagonist-induced fall in both serum and pituitary FSH, but not GnRH receptors, below that observed in the vehicle plus testosterone-treated group. Furthermore, spermatogenesis in the antagonist plus testosterone-treated group was indistinguishable from that observed in control animals. It is concluded that testosterone is capable of maintaining serum and pituitary FSH levels in vivo, under conditions which presumably render the pituitary insensitive to hypothalamic GnRH. J. Endocr. (1986) 108, 101–107

Neonatal glucocorticoid administration: effect on the diurnal rhythm of serum concentrations of corticosterone, progesterone and LH, and the response to pregnant mare serum gonadotrophin in immature female rats

1984 ◽  
Vol 100 (2) ◽  
pp. 203-207 ◽  
Author(s):  
D. R. Mann ◽  
M. Braverman ◽  
I. Cohen ◽  
M. Cost
Keyword(s):  
Diurnal Rhythm ◽  
Ovarian Response ◽  
Female Rats ◽  
Diurnal Changes ◽  
Female Rat ◽  
Serum Concentrations ◽  
Immature Female ◽  
Serum Progesterone ◽  
Serum Corticosterone ◽  
Pregnant Mare Serum Gonadotrophin

ABSTRACT The effects of neonatal cortisol acetate administration on diurnal changes in serum corticosterone, progesterone and LH and on the response to pregnant mare serum gonadotrophin (PMSG) were examined in immature female rats. Neonatal cortisol treatment (250 μg/rat) abolished the diurnal rhythm of serum progesterone in rats at 27—29 days of age, and lowered overall the serum progesterone response to PMSG. Neonatal cortisol also reduced the number of animals ovulating on day 28 after PMSG injection 48 h earlier. This dosage of cortisol did not alter the diurnal rhythm of serum corticosterone in these animals. Serum LH concentrations in control rats at 27–29 days of age did not differ between 09.00 and 18.00 h, and prior treatment with cortisol acetate did not significantly influence serum concentrations of this hormone. Our data suggest that ovarian production of progesterone contributes significantly to diurnal fluctuations of this steroid in the circulation of immature rats. Perinatal exposure to cortisol acetate abolishes the diurnal rhythm of serum progesterone and impairs the ovarian response of the immature female rat to PMSG. The mechanism(s) by which cortisol acetate alters these processes remains to be determined. J. Endocr. (1984) 100, 203–207

STEROL SYNTHESIS IN RATS WITH EXPERIMENTALLY-INDUCED POLYCYSTIC OVARIES

1967 ◽  
Vol 39 (1) ◽  
pp. 53-60 ◽  
Author(s):  
W. C. ADAMS ◽  
J. H. LEATHEM
Keyword(s):  
Serum Cholesterol ◽  
Total Content ◽  
Gonadal Hormones ◽  
Female Rats ◽  
Cholesterol Concentration ◽  
Sterol Synthesis ◽  
Sterol Metabolism ◽  
Polycystic Ovaries ◽  
Immature Female

SUMMARY Immature female rats were fed thiouracil for 30 days and injected with 10 i.u. human chorionic gonadotrophin (HCG) for the last 20 days. In thiouracil-fed animals, HCG produced large ovaries containing follicular cysts. These ovaries showed a subnormal concentration of cholesterol but both a normal total content and normal incorporation of [1-14C]acetate into digitonin-precipitable-sterols. Liver and serum cholesterol concentrations were reduced, but in vivo, 4 hr. incorporation of acetate into sterols was doubled suggesting either an acceleration of cholesterol turnover or delayed utilization of sterol precursors of cholesterol. HCG also reduced ovarian cholesterol concentration in euthyroid animals but total organ content and incorporation of [14C]acetate were not altered, nor were liver and serum cholesterol affected. Since the effect of induced ovarian cysts on sterol metabolism cannot be accounted for by known effects of thyroid or gonadal hormones it is suggested that influences of steroid hormones on lipid metabolism may be greatly modified in thyroid deficiency.

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