INTERACTION BETWEEN OESTROGEN AND GONADOTROPHIN-RELEASING HORMONE ON THE RELEASE AND SYNTHESIS OF LUTEINIZING HORMONE AND FOLLICLE-STIMULATING HORMONE FROM INCUBATED PITUITARIES

1976 ◽  
Vol 68 (1) ◽  
pp. 127-136 ◽  
Author(s):  
MARTA E. APFELBAUM ◽  
S. TALEISNIK
Keyword(s):  
Incubation Medium ◽  
Ovariectomized Rats ◽  
Spontaneous Release ◽  
Dose Response Relationship ◽  
Dual Effect ◽  
Releasing Hormone ◽  
Oestradiol Benzoate ◽  
Pituitary Glands ◽  
Gonadotrophin Releasing Hormone ◽  
Gland Content

SUMMARY The release and synthesis of LH and FSH were studied in adenohypophyses from ovariectomized rats incubated for a period of 4 h in flasks containing 1 ml Eagle's medium. One hemipituitary was used as the experimental gland and the other half served as a control. Glands from ovariectomized untreated animals showed a spontaneous release of LH and FSH and the amount of hormones released (per mg gland) by both the hemipituitaries was not significantly different. Also the content of the hormones at the end of the incubation period was similar in both halves. Gonadotrophin-releasing hormone (Gn-RH) added to the incubation medium stimulated the release of LH and FSH. A dose–response relationship was obtained between doses of 0·51 and 8·00 ng/ml medium. Although lower doses were required to increase the release of LH, the amount of FSH released was higher when expressed as a percentage of gland content. Pituitary glands from ovariectomized rats treated with 5 μg oestradiol benzoate 24 h before being killed showed an increase in sensitivity to Gn-RH, but the response decreased when oestrogen was injected 2 h before death. Also the addition of oestradiol-17β to the incubation medium inhibited LH and FSH release induced by Gn-RH. Gonadotrophin-releasing hormone increased the spontaneous synthesis of LH and FSH observed in the incubated pituitaries. This effect of Gn-RH was stimulated by the injection of oestrogen into the donor animals whereas administration of oestrogen into the medium enhanced the synthesis of LH and partially inhibited that of FSH. These results provide evidence for a dual effect of oestrogen on the release of LH and FSH induced by Gn-RH. They also show that synthesis of gonadotrophic hormones was favoured by oestrogen or by increased gonadotrophin release.

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.

STIMULATORY AND INHIBITORY EFFECTS OF OVARIAN STEROIDS ON GONADOTROPHIN SECRETION IN OVARIECTOMIZED RATS AFTER ANTERIOR HYPOTHALAMIC DEAFFERENTATION

1978 ◽  
Vol 77 (1) ◽  
pp. 11-23 ◽  
Author(s):  
S. TALEISNIK ◽  
L. CALIGARIS ◽  
C. BELTRAMINO ◽  
A. CÁCERES
Keyword(s):  
Arcuate Nucleus ◽  
Anterior Commissure ◽  
Ovariectomized Rats ◽  
Optic Chiasma ◽  
Releasing Hormone ◽  
Hypothalamic Lesions ◽  
Hypothalamic Deafferentation ◽  
Oestradiol Benzoate ◽  
Rcs Rats ◽  
Gonadotrophin Releasing Hormone

The effect of frontal hypothalamic deafferentation on the release of LH and FSH was studied in ovariectomized rats. Frontal cuts were placed just in front of the arcuate nucleus, at the posterior border of the optic chiasma (RCS), at the level of the anterior commissure (POS) and in front of the optic chiasma (PCS). Animals with RCS and POS cuts showed vaginal smears with persistent cornification; the other groups had irregular cycles. The concentrations of LH and FSH in the serum increased after ovariectomy in deafferentated animals, but after 4 weeks the levels were lower than in the animals without hypothalamic lesions except for the PCS group. The more caudally that the cuts were located, the lower were the concentrations of hormones in the serum. The injection of repeated doses of oestradiol benzoate resulted in a decrease in serum gonadotrophin of both rats without hypothalamic lesions and RCS rats. Although a greater decrease was observed in the lesioned than in the intact rats, it is believed that such an effect does not indicate an increased sensitivity of deafferentated animals to this steroid. The stimulatory effect of progesterone on LH and FSH release was studied in ovariectomized rats primed with oestradiol benzoate. The responses were unchanged in PCS animals but failed to occur in POS and RCS rats. Measurement of the level of gonadotrophin-releasing hormone in frontal hypothalamic slices from RCS animals showed a decreased level behind the cut and an increased one in front of it, suggesting that perikarya located in front of the section were sending their axons to the mediobasal hypothalamus. It is believed that the blockade of the stimulatory effect on gonadotrophins by frontal hypothalamic deafferentation is due to the transection of these axons. Cuts placed immediately in front of the arcuate nucleus, however, permitted progesterone-induced gonadotrophin release because of incoming neurones containing gonadotrophin-releasing hormone, which end in structures immediately rostral to the cut. The results indicate that effects of both inhibitory and stimulatory ovarian steroid feedback are impaired by frontal hypothalamic deafferentation.

PITUITARY SENSITIVITY TO GONADOTROPHIN RELEASING HORMONE AFTER HYPERPROLACTINAEMIA INDUCED WITH NEUROLEPTICS AND DOMPERIDONE IN THE RAT

1981 ◽  
Vol 91 (3) ◽  
pp. 439-446 ◽  
Author(s):  
D. A. CARTER ◽  
S. A. WHITEHEAD
Keyword(s):  
Ovariectomized Rats ◽  
Dopamine Antagonists ◽  
Dopamine Antagonist ◽  
Releasing Hormone ◽  
Pituitary Glands ◽  
Drug Treatments ◽  
Gonadotrophin Releasing Hormone ◽  
High Concentrations ◽  
Perifusion System ◽  
Intact Rats

The effect of hyperprolactinaemia induced by dopamine-antagonist drugs on pituitary responsiveness to gonadotrophin releasing hormone (Gn-RH) and on plasma LH levels has been investigated in intact and ovariectomized rats. The animals were pretreated with haloperidol, pimozide or domperidone and the sensitivity of isolated pituitary glands to pulses of Gn-RH were tested using a perifusion system. Trunk blood, collected at the time of killing, was assayed for plasma LH and prolactin. In addition, a direct effect of the drugs on pituitary responsiveness to Gn-RH was investigated by perifusing pituitary glands taken from untreated, pro-oestrous rats in medium containing the dopamine antagonists. The pituitary responsiveness was significantly impaired in intact rats after treatment with each of the drugs whereas no effect was observed in pretreated ovariectomized rats. None of the drug treatments altered levels of circulating LH. High concentrations of the drugs present in the perifusion medium also inhibited pituitary responsiveness although it is not known whether the concentrations of the drugs present in the pretreated animals would exert a similar effect. The results suggest that short-term hyperprolactinaemia impairs pituitary responsiveness through a modulation of ovarian steroid secretion and that Gn-RH release is not altered. Treatment with domperidone exhibited similar effects on the parameters measured here to those caused by the two neuroleptics, indicating that this novel anti-dopaminergic drug is acting in a similar manner.

Inducing ovulation with oestradiol cypionate allows flexibility in the timing of insemination and removes the need for gonadotrophin-releasing hormone in timed AI protocols for dairy cows

2017 ◽  
Vol 29 (3) ◽  
pp. 468 ◽  
Author(s):  
R. M. Ferreira ◽  
H. Ayres ◽  
L. U. Gimenes ◽  
F. P. Torres ◽  
F. A. Lima ◽  
...  
Keyword(s):  
Dairy Cows ◽  
Pregnancy Rates ◽  
Holstein Cows ◽  
Device Removal ◽  
Releasing Hormone ◽  
Ovulatory Follicle ◽  
Oestradiol Benzoate ◽  
Gonadotrophin Releasing Hormone

The effects of addition of gonadotrophin-releasing hormone (GnRH) to a progesterone plus oestradiol-based protocol and timing of insemination in Holstein cows treated for timed AI (TAI) were evaluated. Cows (n = 481) received a progesterone device and 2 mg oestradiol benzoate. After 8 days, the device was removed and 25 mg dinoprost was administered. Cows were allocated to one of three (Study 1; n = 57) or four (Study 2; n = 424) groups, accordingly to ovulation inducer alone (Study 1; oestradiol cypionate (EC), GnRH or both) or ovulation inducer (EC alone or combined with GnRH) and timing of insemination (48 or 54 h after device removal; Study 2). In Study 1, the diameter of the ovulatory follicle was greater for GnRH than EC. Oestrus and ovulation rates were similar regardless of ovulatory stimuli. However, time to ovulation was delayed when GnRH only was used. In Study 2, cows treated with GnRH or not had similar pregnancy per AI (P/AI) 30 days (41.5% vs 37.3%; P = 0.28) and 60 days (35.9% vs 33.0%; P = 0.61) after TAI. TAI 48 and 54 h after device removal resulted similar P/AI at 30 days (40.3% vs 38.5%; P = 0.63) and 60 days (33.8% vs 35.1%; P = 0.72). Thus, adding GnRH at TAI does not improve pregnancy rates in dairy cows receiving EC. The flexibility of time to insemination enables TAI of a large number of cows using the same protocol and splitting the time of AI.

Infantile ovariectomy potentiates the stimulatory effect of oestrogen/progesterone on LH secretion in the rat

1985 ◽  
Vol 106 (1) ◽  
pp. 133-139 ◽  
Author(s):  
M. Wilkinson ◽  
R. Bhanot
Keyword(s):  
Inhibitory Mechanism ◽  
Releasing Hormone ◽  
Oestradiol Benzoate ◽  
Gonadotrophin Releasing Hormone ◽  
Prepubertal Rats ◽  
Lh Secretion

ABSTRACT Ovariectomy of prepubertal rats (9 days of age) eliminates the ability of the opiate peptide FK 33-824 to inhibit LH secretion when tested 19 days later. We have investigated whether this removal of opiate inhibition would modify the LH/FSH response to stimulation with oestradiol benzoate/progesterone priming. Ovariectomy of rats during infancy (9 days after birth) amplifies the stimulatory effects of these steroids on LH/FSH secretion when tested 19 days later. This amplification was not seen in rats ovariectomized before (day 24) or after puberty (day 43) and tested 19 days later. The pituitary content of LH/FSH does not appear to contribute to this phenomenon, though increased responsiveness to injected gonadotrophin-releasing hormone (GnRH) is clearly involved; ovariectomy at day 9 is considerably more effective than ovariectomy at day 24 of life in enhancing the response to GnRH. We conclude that infantile ovariectomy either removes, or prevents the development of, a hypothalamic inhibitory mechanism which normally modulates the responsiveness of the pituitary to stimulation with GnRH. J. Endocr. (1985) 106, 133–139

Effects of pituitary-gonadal suppression with a gonadotrophin-releasing hormone agonist on fetal gonadotrophin secretion, fetal gonadal development and maternal steroid secretion in the sheep

1994 ◽  
Vol 141 (2) ◽  
pp. 317-324 ◽  
Author(s):  
G B Thomas ◽  
A S McNeilly ◽  
F Gibson ◽  
A N Brooks
Keyword(s):  
Gnrh Agonist ◽  
Fetal Development ◽  
Plasma Concentrations ◽  
Gonadal Development ◽  
Maternal Circulation ◽  
Biodegradable Implant ◽  
Steroid Secretion ◽  
Releasing Hormone ◽  
Pituitary Glands ◽  
Gonadotrophin Releasing Hormone

Abstract In order to investigate the regulation of the hypothalamo-pituitary-gonadal axis during fetal development, sheep fetuses at day 70 of gestation were implanted subcutaneously with a biodegradable implant containing the longacting gonadotrophin-releasing hormone (GnRH) agonist, buserelin. The treatment of fetuses with a GnRH agonist throughout the last half of gestation (term=145 days) abolished the increase in plasma LH concentrations that was seen in 2-day-old control lambs in response to an injection of GnRH. This attenuated response was associated with corresponding reductions in the pituitary content of LH and FSH. Immunolocalization studies revealed that pituitary glands from newborn lambs implanted with a GnRH agonist during fetal development were devoid of immunopositive LH- and FSH-containing cells. At birth the testicular weights of GnRH agonist-treated ram lambs were significantly decreased by 40% when compared with controls. This was associated with a 45% reduction in the total number of Sertoli cells per testis. In newborn ewe lambs GnRH agonist treatment had no effect on ovarian weight or on the morphological appearance of the ovaries. GnRH agonist treatment had no effect on the plasma concentrations of progesterone and oestrone in the maternal circulation or on the length of gestation. These results show (1) that GnRH positively regulates the synthesis and secretion of gonadotrophins in the fetus, (2) that reduced fetal gonadotrophic support during the last half of gestation results in a reduction in testicular growth, and (3) that fetal gonadotrophins do not affect maternal steroid secretion. Journal of Endocrinology (1994) 141, 317–324

scholarly journals The reproductive performance of dairy cows with anovulatory anoestrus that were injected with either gonadotrophin-releasing hormone or oestradiol benzoate as part of a re-treatment process after insemination

2007 ◽  
Vol 78 (1) ◽  
Author(s):  
B.V.E. Segwagwe ◽  
J. Malmo ◽  
K.L. Macmillan ◽  
P.D. Mansell
Keyword(s):  
Dairy Cows ◽  
Pregnancy Rate ◽  
Reproductive Performance ◽  
Conception Rate ◽  
Control Group ◽  
Releasing Hormone ◽  
Start Date ◽  
Oestradiol Benzoate ◽  
Conception Rates ◽  
Gonadotrophin Releasing Hormone

This experiment compared the reproductive performance of synchronised anoestrous dairy cows that were treated initially with a combination of progesterone and oestradiol benzoate and then with either gonadotrophin-releasing hormone (GnRH) or oestradiol benzoate to resynchronise returns to service. It was hypothesised that injecting anoestrous dairy cows with GnRH 12-15 days after insemination and coinciding with the time of insertion of a controlled intravaginal progesterone-releasing (CIDR) device would increase conception rates to the preceding 1st insemination compared with oestradiol benzoate treated cows; both GnRH and oestradiol benzoate would resynchronising the returns to service of those cows that did not conceive to the preceding insemination. Groups of cows in 11 herds were presented for a veterinary examination after they had not been seen in oestrus postpartum. Those cows diagnosed with anovulatory anoestrus (n = 1112) by manual rectal palpation and / or ultrasonography were enrolled in the trial. Each enrolled cow was injected with 2mg oestradiol benzoate i.m. on Day -10, (where Day 0 was the 1st day of the planned insemination) concurrently with vaginal insertion of a CIDR device. The device inserted was withdrawn on Day -2 and then each cow injected i.m. with 1 mg of oestradiol benzoate on Day -1 unless it was in oestrus. Observation for oestrus preceded each insemination. Every cow that had been inseminated on Days -1,0,1 or 2 was presented for treatment for resynchrony on Day 14 (n=891). They were divided into 2 groups; those with an even number were each injected i.m. with 250 µg of a GnRH agonist (Treatment group n = 477); each of the cows with an odd number injected i.m. with 1mg of oestradiol benzoate (control group, n = 414). Each GnRH or oestradiol benzoate injection preceded reinsertion of a CIDR device previously inserted from Days -10 to -2. It was withdrawn on Day 22, 24 hours before injecting 1mg oestradiol benzoate. Cows observed in oestrus were submitted for a 2nd insemination. Every enrolled cow still present in the herd was pregnancy tested by palpation of uterine contents per rectum about 6 weeks later and again at the end of a herd's seasonal breeding programme. The alternative use of GnRH instead of oestradiol benzoate did not affect the percentage of cows conceiving within 3 days of the mating start date (MSD) (35.6 %vs 35.3 %, P=0.90), resubmission rates for a 2nd insemination among cows not pregnant to the 1st insemination (81.6 % vs 83.5 %, P=0.41), 6-week pregnancy rate (59.3 % vs 60.6 %, P=0.65), 21-week pregnancy rate (86.6 vs 85.0, P=0.36), mean interval from MSD to conception (32.5 + 1.8 days vs 29.9 + 1.8 days, P = 0.26) or conception rate of cows reinseminated by Day 28 (43.3 % vs 38.8 %, P=0.39). When GnRH conception rate of cows reinseminated by Day 28 (43.3% vs was compared with oestradiol benzoate, it did not increase conception rates to the 1st service; it was as effective as oestradiol benzoate in synchronising returns to service in previously treated anoestrous cows that did not conceive to the 1st service. Its use affected neither conception rates to the preceding 1st inseminations nor to the following 2nd inseminations.

SECRETION OF LUTEINIZING HORMONE CAUSED BY CONTINUOUS INFUSIONS OF LUTEINIZING HORMONE RELEASING HORMONE IN THE LONG-TERM OVARIECTOMIZED RAT: EFFECT OF OESTROGEN PRETREATMENT

1976 ◽  
Vol 71 (1) ◽  
pp. 1-11 ◽  
Author(s):  
G. A. SCHUILING ◽  
H. P. GNODDE
Keyword(s):  
Luteinizing Hormone ◽  
Pituitary Gland ◽  
Ovariectomized Rats ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Clear Cut ◽  
Oestradiol Benzoate ◽  
Maximal Plasma ◽  
Lh Rh

SUMMARY Continuous infusions of luteinizing hormone releasing hormone (LH-RH) into phenobarbitone-treated long-term ovariectomized rats, resulted in patterns of LH secretion which were determined by the blood LH-RH concentration. Infusions of 52 ng LH-RH/h caused steadily increasing plasma LH levels, which stabilized after about 2 h of infusion and were maintained for the rest of the experiment (9 h). A similar course of plasma LH concentration was observed as a result of infusions of 104 ng LH-RH/h, though in this case LH concentrations reached higher levels than those induced by infusion of 52 ng LH-RH/h. Higher rates of LH-RH infusion (208 and 416 ng/h), however, induced clear-cut LH peaks, which reached their maximal plasma values after 2–3 h of infusion and then declined again until, at the end of the experiment, they were only slightly higher than the LH levels induced by infusions of 52 ng LH-RH/h. A similar series of LH-RH infusions given to ovariectomized rats pretreated with oestradiol benzoate during 3 days (the rats were injected daily with 7 μg steroid), produced a highly augmented response of the pituitary gland, but all LH-RH concentrations infused induced rather sharp LH peaks, reaching their maximum after 2–3 h of infusion. After 5 h of infusion the descending parts of all these peaks appeared to converge. In both control and oestradiol benzoate-pretreated rats there appeared to be a linear relationship between the logarithm of the blood LH-RH concentration and the maximal plasma LH values on one hand, and the amount of LH secreted during the first 5 h of infusion on the other. Furthermore, it appeared that the longer the period of oestrogen action, the more the response of the pituitary gland to a certain dose of LH-RH was enhanced.

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

1977 ◽  
Vol 86 (4) ◽  
pp. 704-713 ◽  
Author(s):  
Marta E. Apfelbaum ◽  
S. Taleisnik
Keyword(s):  
Incubation Medium ◽  
Additive Effects ◽  
Spontaneous Release ◽  
Oestrogen Treatment ◽  
Gonadotrophin Secretion ◽  
Oestradiol Benzoate ◽  
Dose Dependent

ABSTRACT The effect of oestrogen on the release and synthesis of LH and FSH was studied in rat adenohypophyses incubated for a period of 4 h in flasks containing 1 ml Eagle's medium. One hemipituitary was used as the experimental gland and the other half served as a control. The spontaneous release of LH and FSH by glands from ovarectomized rats was not affected by oestradiol-17β added to the incubation medium in doses of 55, 166, 500 and 1500 ng/ml. The amount of hormones released by pituitaries from spayed rats injected with oestradiol benzoate (2.5, 5.0 and 10.0 μg/rat) 2 h or 24 h before killing the animals too was not different from that of oil-injected rats. Neither was there any effect of oestrogen when added to the incubation medium of glands from oestrogen-pre-treated rats. However, the concentration of LH and FSH in the gland increased when oestrogen was added to the incubation medium, indicating enhanced synthesis. The effect was dose-dependent up to the dose of 500 ng/ml oestradiol but a dose of 1500 ng/ml was less effective. Increased synthesis of LH but not of FSH was also observed in incubated glands from rats injected with oestrogen 24 h before death, but no changes were seen in those of rats killed 2 h after treatment. Additive effects occurred with the in vivo and in vitro steroid treatment. These results indicate that oestrogen favours synthesis of LH and FSH in cultured pituitaries, without affecting gonadotrophin secretion and that the changes induced in the in situ gland by oestrogen treatment are reflected by their in vitro activity.

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