GONADOTROPHIN RELEASE IN HYPOGONADAL AND NORMAL MICE AFTER ELECTRICAL STIMULATION OF THE MEDIAN EMINENCE OR INJECTION OF LUTEINIZING HORMONE RELEASING HORMONE

1980 ◽  
Vol 85 (1) ◽  
pp. 105-110 ◽  
Author(s):  
CAROL A. IDDON ◽  
H. M. CHARLTON ◽  
G. FINK
Keyword(s):  
Electrical Stimulation ◽  
Pituitary Gland ◽  
Median Eminence ◽  
Normal Male ◽  
Male Mice ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Lh Rh ◽  
Lh Releasing Hormone ◽  
Stimulation Of

SUMMARY Electrical stimulation of the median eminence, using parameters known to cause the release of LH in normal male mice, failed to elicit any gonadotrophin response in hypogonadal (hpg) male mice. Administration of 40 ng synthetic LH releasing hormone (LH-RH) resulted in release of LH from the pituitary gland of hpg mice, although the response was significantly lower than that of normal mice. These results were consistent with the hypothesis that the hypogonadal state of the hpg mouse results from a functional absence of LH-RH in the hypothalamus rather than from a lack of response of the pituitary gland to the releasing hormone.

POSSIBLE PRIMING EFFECT OF LUTEINIZING HORMONE RELEASING HORMONE ON THE ANTERIOR PITUITARY GLAND IN THE JAPANESE QUAIL AND THE STIMULATION OF SECRETION OF FOLLICLE-STIMULATING HORMONE

1979 ◽  
Vol 82 (1) ◽  
pp. 71-75 ◽  
Author(s):  
D. T. DAVIES ◽  
J. COLLINS
Keyword(s):  
Pituitary Gland ◽  
Japanese Quail ◽  
Anterior Pituitary ◽  
Follicle Stimulating Hormone ◽  
Anterior Pituitary Gland ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Lh Rh ◽  
Lh Releasing Hormone ◽  
Stimulation Of

SUMMARY After the i.m. injection of 10 μg synthetic LH releasing hormone (LH-RH) into Japanese quail the levels of LH and FSH in plasma rose significantly within 2 min. The increased level of LH declined rapidly but that of FSH was maintained for the duration of the experiment. To determine whether the anterior pituitary gland is primed by LH-RH a double injection schedule was adopted. It would appear that, while endogenous LH-RH may prime the avian pituitary gland slightly, synthetic LH-RH is ineffective.

Priming effect of luteinizing hormone releasing hormone in the hypogonadal mouse

1982 ◽  
Vol 94 (2) ◽  
pp. 283-287 ◽  
Author(s):  
G. Fink ◽  
W. J. Sheward ◽  
H. M. Charlton
Keyword(s):  
Luteinizing Hormone ◽  
Pituitary Gland ◽  
Priming Effect ◽  
Plasma Concentrations ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Lh Rh ◽  
Lh Releasing Hormone

We have investigated the LH response to LH releasing hormone (LH-RH) in female hypogonadal (hpg) mice in which the hypothalamus contains no LH-RH and the pituitary gland contains significantly less LH than in normal mice. Both the releasing action and the priming effect of LH-RH were not significantly different in hpg compared with normal mice. Raised plasma concentrations of oestradiol-17β reduced pituitary responsiveness to LH-RH in normal but not in hpg mice. These results show that in the mouse neither longterm exposure to normal levels of LH-RH nor a normal pituitary content of LH are necessary for either the releasing or the priming action of LH-RH.

EFFECT OF CORTISOL OR ADRENOCORTICOTROPHIN ON RELEASE OF LUTEINIZING HORMONE INDUCED BY LUTEINIZING HORMONE RELEASING HORMONE IN THE DAIRY HEIFER

1982 ◽  
Vol 92 (1) ◽  
pp. 141-146 ◽  
Author(s):  
R. L. MATTERI ◽  
G. P. MOBERG
Keyword(s):  
Luteinizing Hormone ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Dairy Heifers ◽  
Significant Difference ◽  
Significant Depression ◽  
Lh Rh ◽  
Lh Releasing Hormone ◽  
And Control ◽  
Slight Depression

During treatment with cortisol or ACTH, dairy heifers were given two doses of LH releasing hormone (LH-RH) spaced 1·5 h apart. Serum concentrations of cortisol and LH were monitored during each treatment. Treatment with both ACTH and cortisol raised plasma cortisol levels above the respective saline controls (P<0·001). Neither treatment affected basal LH concentrations. A slight depression in LH response was seen in the cortisol-treated animals after the first LH-RH injection, as shown by a statistically significant depression at three of the sample times. There was no significant difference between treated and control LH values after the second LH-RH administration. Treatment with ACTH resulted in significantly reduced LH values at all sample times after both injections of LH-RH.

LUTEINIZING HORMONE RELEASING HORMONE-INDUCED RELEASE OF LUTEINIZING HORMONE FROM PITUITARY EXPLANTS OF COWS KILLED BEFORE OR AFTER OESTRADIOL TREATMENT

1981 ◽  
Vol 88 (1) ◽  
pp. 17-25 ◽  
Author(s):  
E. M. CONVEY ◽  
J. S. KESNER ◽  
V. PADMANABHAN ◽  
T. D. CARRUTHERS ◽  
T. W. BECK
Keyword(s):  
Luteinizing Hormone ◽  
Pituitary Gland ◽  
Lh Surge ◽  
Releasing Hormone ◽  
Oestradiol Treatment ◽  
Readily Releasable Pool ◽  
Serum Lh ◽  
Pituitary Glands ◽  
Lh Rh ◽  
Lh Releasing Hormone

In ovariectomized heifers, oestradiol decreases concentrations of LH in serum for approximately 12 h after which LH is released in a surge comparable in size and duration to the preovulatory surge. Using this model, we measured LH release induced by LH releasing hormone (LH-RH) from pituitary explants taken from ovariectomized heifers before or after an oestradiol-induced LH surge. These changes were related to changes in LH concentrations in serum and pituitary glands and hypothalamic LH-RH content. Twenty Holstein heifers were randomly assigned to one of four treatment groups to be killed 0, 6, 12, or 24 h after the injection of 500 μg oestradiol-17β. Jugular blood was collected at −2, −1 and 0 h then at intervals of 2 h until slaughter. Pituitary glands were collected and ≃2 mm3 explants were exposed to 4 ng LH-RH/ml medium for 30 min (superfusion) or 4 ng LH-RH/ml medium for 2 h in Erlenmeyer flasks. Levels of LH were measured in the medium. Hypothalami, collected at autopsy, were assayed for LH-RH content. To determine pituitary LH content, an additional 15 ovariectomized heifers were killed, five each at 0, 12 and 24 h after the injection of 500 μg oestradiol. In both groups of heifers, oestradiol reduced serum LH concentrations to ≃ 1 ng/ml, a level which persisted for 12 h, when LH was released in a surge. Pituitary sensitivity to LH-RH was increased at 6 and 12 h after the injection of oestradiol, but was markedly decreased at 24 h, i.e. after the LH surge. Despite this twofold increase in capacity of the pituitary gland to release LH in response to LH-RH, pituitary LH content did not change during 12 h after oestradiol treatment. However, LH content decreased after the LH surge and this decrease was associated with a decrease in pituitary responsiveness to LH-RH. Hypothalamic LH-RH content was not altered by these treatments. We have interpreted our results as evidence that oestradiol exerts a positive feedback effect on the pituitary gland of ovariectomized heifers such that pituitary sensitivity to LH-RH is increased twofold by the time the LH surge is initiated. In addition, oestradiol causes a transitory inhibition of LH-RH release as shown by the fact that serum LH concentrations remained low during the interval from injection of oestradiol until the beginning of the LH surge despite the fact that pituitary sensitivity to LH-RH is increased at this time. Depletion of a readily releasable pool of pituitary LH may be the mechanism by which the LH surge is terminated.

OESTRADIOL STIMULATION OF PROLACTING RELEASE FROM CANINE PITUITARY IN CULTURE

1976 ◽  
Vol 82 (3) ◽  
pp. 706-709 ◽  
Author(s):  
Gwyneth E. Jones ◽  
A. R. Boyns
Keyword(s):  
Tissue Culture ◽  
Luteinizing Hormone ◽  
Prolactin Release ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Thyrotrophic Hormone ◽  
Lh Rh ◽  
Stimulation Of

ABSTRACT Anterior canine pituitaries were maintained in tissue culture for 8 days, and the immunoreactive prolactin released, was measured by a heterologous radioimmunoassay for canine prolactin. Luteinizing hormone-releasing hormone (LH-RH) and thyrotrophic hormone-releasing hormone (TRH) did not affect prolactin release, while theophylline and oestradiol-17β stimulated the release of canine prolactin.

EFFECT OF SYNTHETIC LUTEINIZING HORMONE RELEASING HORMONE ON OVULATION DURING THE OESTROUS CYCLE IN THE RAT

1974 ◽  
Vol 76 (3) ◽  
pp. 431-437 ◽  
Author(s):  
H. Morishita ◽  
H. Mitani ◽  
Y. Masuda ◽  
K. Higuchi ◽  
M. Tomioka ◽  
...  
Keyword(s):  
Luteinizing Hormone ◽  
Pituitary Gland ◽  
Critical Period ◽  
Early Period ◽  
Oestrous Cycle ◽  
Female Rats ◽  
Average Volume ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Lh Rh

ABSTRACT The effect of synthetic luteinizing hormone releasing hormone (LH-RH) on ovulation has been studied during the oestrous cycle in adult female rats. Ovulation could be induced by the administration of 1 μg synthetic LH-RH at 1:00 a. m. on the day of dioestrus II (lights on from 10:00 p.m. to 10:00 a.m.). At 1:00 a.m. on the day of dioestrus II, the average volume of the largest follicles reached a volume of 83 × 106 μm3 and was three fifth of the volume of that at 6:00 a. m. on the day of pro-oestrus (critical period). These findings suggest that the luteinizing hormone (LH) content in the pituitary gland during the early period of dioestrus II is sufficient to induce ovulation and that the follicles that reach to three fifth of the volume at the critical period are capable of ovulating providing endogenous ovulatory LH released.

STUDIES WITH FRAGMENTS OF A HIGHLY ACTIVE ANALOGUE OF LUTEINIZING HORMONE RELEASING HORMONE

1979 ◽  
Vol 81 (2) ◽  
pp. 175-182 ◽  
Author(s):  
J. SANDOW ◽  
W. KÖNIG
Keyword(s):  
Luteinizing Hormone ◽  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Enzyme Stability ◽  
Organ Distribution ◽  
Structural Requirements ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Highly Active ◽  
Lh Rh

The minimal structural requirements for gonadotrophin releasing activity were studied with fragments of a highly active analogue of luteinizing hormone releasing hormone (LH-RH), [d-Ser(But)6]LH-RH(1–9)nonapeptide-ethylamide (Hoe 766). All fragments are related to the C-terminal structure of LH-RH and have increased enzyme stability. Ovulation in phenobarbitone-blocked rats was induced with a median effective dose/rat, of 1·9 μg of the (3–9)-heptapeptide, Trp-Ser-Tyr-d-Ser(But)-Leu-Arg-Pro-ethylamide and 6·8, 18·0 and 38·3 μg for the (4–9), (5–9) and (6–9) fragments respectively. The (3–9)-heptapeptide and (4–9)-hexapeptide induced release of LH and FSH in phenobarbitone-blocked rats with a ratio similar to that of LH-RH. Degradation of LH-RH by enzyme preparations of liver, kidney and hypothalamic or anterior pituitary tissue was not modified by addition of the (3–9)-heptapeptide fragment. The organ distribution of the 125I-labelled (3–9)-heptapeptide fragments was similar to LH-RH, but not to Hoe 766. The peptide accumulated in liver and kidney, but was eliminated from the anterior pituitary gland 15 min after i.v. injection, whereas Hoe 766 showed progressive accumulation in the pituitary gland (tissue: plasma ratio = 6·6 after 60 min). In contrast to C-terminal fragments of LH-RH, the corresponding fragments of nonapeptide analogues retained significant biological activity, and the minimal structural requirements for LH release may be related to the C-terminal sequence of LH-RH.

STIMULATION OF RELEASE OF LUTEINIZING HORMONE FROM CULTURED PITUITARY CELLS BY 2- AND 4-HYDROXYLATED OESTROGENS

1981 ◽  
Vol 90 (3) ◽  
pp. 433-436 ◽  
Author(s):  
S. FRANKS ◽  
G. R. MERRIAM ◽  
CYNTHIA G. GOODYER ◽  
F. NAFTOLIN
Keyword(s):  
Luteinizing Hormone ◽  
Anterior Pituitary ◽  
Monolayer Culture ◽  
Pituitary Cells ◽  
Releasing Hormone ◽  
Oestradiol Treatment ◽  
Lh Rh ◽  
Lh Releasing Hormone ◽  
Stimulation Of

We have examined the effects of the catechol oestrogens 2-hydroxyoestradiol (2-OHE2), 4-hydroxyoestradiol (4-OHE2) and 2-hydroxyoestrone (2-OHE1) and their corresponding primary oestrogens on secretion of LH and FSH by enzymatically dispersed rat anterior pituitary cells in monolayer culture. Basal LH levels in the medium were significantly higher than in control wells when cells were exposed to 10−8m-oestradiol-17β for 40 h: oestrone and all three catechol oestrogens (in the same doses) also stimulated basal LH concentrations to levels quantitatively similar to those seen after oestradiol treatment. The same effects were observed when steroids were given at 10−9 mol/l. Oestradiol, 2-OHE2, and 4-OHE2 but not 2-OHE1 increased pituitary responsiveness to LH releasing hormone (LH-RH) (given in a range of doses from 10−11 to 10−6 mol/l). The responses of cells treated with 2-OHE2 and 4-OHE2 were similar, though less than the response seen after treatment with oestradiol. This contrasts with the very different oestrogenic effects of 2- and 4-OHE2 previously observed in vivo. Neither oestradiol nor the catechol oestrogens had any effect on basal or LH-RH-stimulated FSH release.

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