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.

ONTOGENY OF THE SENSITIZING EFFECT OF OESTRADIOL AND LUTEINIZING HORMONE RELEASING HORMONE ON THE ANTERIOR PITUITARY GLAND OF THE FEMALE RAT

1981 ◽  
Vol 91 (2) ◽  
pp. 347-351 ◽  
Author(s):  
R. MEIDAN ◽  
G. FINK ◽  
Y. KOCH
Keyword(s):  
Luteinizing Hormone ◽  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Priming Effect ◽  
Anterior Pituitary Gland ◽  
Female Rats ◽  
Facilitatory Effect ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Lh Rh

The ontogeny of the facilitatory effect of oestradiol and luteinizing hormone releasing hormone (LH-RH) on the responsiveness of the anterior pituitary gland to LH-RH has been studied in vitro using pituitary glands from female rats aged 15, 17, 20, 31, 35 and 38 days. The facilitatory effect of oestradiol was already well established by day 15, while the facilitatory effect of LH-RH (priming effect) developed only after day 17. Although it increased the overall response of the gland to LH-RH, oestradiol did not selectively enhance the priming effect of LH-RH. Both the effect of oestradiol and LH-RH reached a peak on day 25, 7 days before vaginal opening in this colony, and, as assessed by measuring pituitary LH contents, were not dependent upon the synthesis of LH. These data show that different mechanisms may be involved in the facilitation of pituitary responsiveness by oestradiol and LH-RH, but that both mechanisms appear to depend more upon an increase in the sensitivity of the receptor/release apparatus rather than in the gonadotrophin content of the gonadotrophs.

CHANGES IN RESPONSIVENESS OF DISPERSED PITUITARY CELLS TO LUTEINIZING HORMONE RELEASING HORMONE AT DIFFERENT TIMES OF THE OESTROUS CYCLE OF THE RAT

1981 ◽  
Vol 89 (1) ◽  
pp. 129-134 ◽  
Author(s):  
ALISON SPEIGHT ◽  
G. FINK
Keyword(s):  
Luteinizing Hormone ◽  
Oestrous Cycle ◽  
Female Rats ◽  
Pituitary Cells ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Close Relationship ◽  
Specific Receptors ◽  
Lh Rh

Dispersed pituitary cells obtained from female rats with regular oestrous cycles were suspended in Bio-Gel columns and perfused with pulses of luteinizing hormone releasing hormone (LH-RH). There was a close relationship between the amount of LH released and the concentration of LH-RH in the perfusate. It was not possible to elicit the priming effect of LH-RH, but the LH-response changed markedly during the oestrous cycle in a manner similar to that seen in vivo; i.e. the responses of cells prepared from rats killed at pro-oestrus were much greater than the responses of cells prepared from rats killed on other days of the cycle. A similar change in responsiveness was obtained when the columns were perfused with 60 mmol K+/1, suggesting that at least part of the increase in pituitary responsiveness that occurs at pro-oestrus is not dependent upon changes in specific receptors for LH-RH.

PROLONGED RELEASE BY DIOESTROUS RATS OF FOLLICLE-STIMULATING HORMONE DURING THE PERIOD OF OVULATION INDUCED BY LUTEINIZING HORMONE RELEASING HORMONE

1979 ◽  
Vol 81 (1) ◽  
pp. 109-118 ◽  
Author(s):  
SHUJI SASAMOTO ◽  
SHIGEO HARADA ◽  
KAZUYOSHI TAYA
Keyword(s):  
Luteinizing Hormone ◽  
Plasma Concentrations ◽  
High Plasma ◽  
Oestrous Cycle ◽  
Prolonged Release ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Follicular Maturation ◽  
Lh Rh ◽  
Premature Ovulation

When 1·0 μg luteinizing hormone releasing hormone (LH-RH) was given i.v. three times at 1 h intervals from 17.00 to 19.00 h on the day of dioestrus (day 0) to regular 4 day cyclic rats, premature ovulation was induced the next morning (day 1) with the number of ova present comparable to normal spontaneous ovulation. The next spontaneous ovulation occurred on the morning of day 5, 4 days after premature ovulation induced by LH-RH. Plasma concentrations of FSH and LH showed transient rises and falls within 1 h of administration of LH-RH; concentrations of FSH in the plasma decreased from 20.00 h on day 0 but markedly increased again from 23.00 h on day 0 to 02.00 h on day 1 and these high levels persisted until 14.00 h on day 1, with only a small increase of plasma LH during this period. The duration of increased FSH release during premature ovulation induced by LH-RH treatment was 6 h longer than the FSH surge occurring after administration of HCG on day 0. Surges of gonadotrophin were absent on the afternoon of day 1 (the expected day of pro-oestrus) and the surges characteristic of pro-oestrus occurred on the afternoon of day 4 and ovulation followed the next morning. The pituitary content of FSH did not decrease despite persisting high plasma levels of FSH during premature ovulation induced by either LH-RH or HCG on day 0. The changes in uterine weight indicated that the pattern of oestrogen secretion from the day of premature ovulation induced by LH-RH to the day of the next spontaneous ovulation was similar to that of the normal 4 day oestrous cycle. When 10 i.u. HCG were given on day 0, an increase in oestrogen secretion occurred on day 2, 1 day earlier than in the group given LH-RH on day 0. This advancement of oestrogen secretion was assumed to be responsible for the gonadotrophin surges on day 3. Similar numbers of fully developed follicles were found by 17.00 h on day 2 after premature ovulation induced by either LH-RH or HCG, suggesting that the shorter surge of FSH during premature ovulation induced by HCG had no serious consequences on the initiation of follicular maturation for the succeeding oestrous cycle in these rats. Administration of LH-RH on day 0 had no direct effect on the FSH surge during premature ovulation. Secretory changes in the ovary during ovulation may be responsible for this prolonged selective release of FSH.

SERUM LUTEINIZING HORMONE AND FOLLICLE-STIMULATING HORMONE CONCENTRATIONS IN IMMATURE FEMALE RATS TREATED WITH MULTIPLE INJECTIONS AND VARIOUS AMOUNTS OF LUTEINIZING HORMONE RELEASING HORMONE

1975 ◽  
Vol 66 (1) ◽  
pp. 13-20 ◽  
Author(s):  
D. C. JOHNSON ◽  
R. S. MALLAMPATI
Keyword(s):  
Luteinizing Hormone ◽  
Constant Stimulus ◽  
Female Rats ◽  
Intact Female ◽  
Immature Female ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Serum Luteinizing Hormone ◽  
Serum Lh ◽  
Lh Rh

SUMMARY Release of immunoreactive LH and FSH was induced in immature intact female rats by repeated injections of synthetic luteinizing hormone releasing hormone (LH-RH). Altering the dose of LH-RH (5, 10, 20, 50 ng) and the frequency of administration (every 10, 20, 30 or 60 min) over a period of 2 h produced a variety of serum LH and FSH concentrations and ratios. When the dose was a constant 20 ng but the frequency of injections was either 20 or 30 min, a steady state in serum gonadotrophin concentrations was reached within 1 h and the level remained the same during the second hour. When given every 10 min, 20 ng LH-RH produced a much higher concentration of both LH and FSH during the second hour of stimulation. Examination of the gonadotrophin levels after each injection of LH-RH showed that the pituitary response was variable in spite of a constant stimulus.

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.

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.

LUTEINIZING HORMONE RESPONSIVENESS TO LUTEINIZING HORMONE RELEASING HORMONE IN THE ADULT GUINEA-PIG: DIRECT OVARIAN INVOLVEMENT

1978 ◽  
Vol 76 (1) ◽  
pp. 49-61 ◽  
Author(s):  
M. B. TER HAAR
Keyword(s):  
Luteinizing Hormone ◽  
Guinea Pig ◽  
Oestrous Cycle ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Maximum Increment ◽  
Lh Rh ◽  
Dose Dependent ◽  
Ovarian Involvement ◽  
Stimulation Of

SUMMARY The effects of intravenous injection of synthetic luteinizing hormone releasing hormone (LH-RH) on the release of LH and FSH have been studied in the adult guinea-pig. In all the experiments the secretion of FSH was apparently unaffected by administration of LH-RH. The release of LH was log dose-dependent over the range 0·5–50 μg LH-RH. During the female cycle, the maximum increment in the concentration of LH after a single i.v. injection of 0·5 μg LH-RH decreased progressively from day 1 to day 13. Double or triple injections of 1 μg LH-RH at 1 h intervals produced no potentiation on day 3 but progressively greater LH responses occurred on days 7, 10 or 13 of the oestrous cycle. Ovariectomy immediately before the first injection of LH-RH on day 7 blocked the potentiated response to subsequent injections, whereas ovariectomy immediately before the second injection still permitted this potentiation. These results suggest that there is direct ovarian involvement in the potentiated response to LH-RH observed during the later part of the guinea-pig oestrous cycle. Infusion of LH-RH (1 μg over 200 min) produced a potentiated release of LH in female guinea-pigs on day 7 (but not on day 3) of the oestrous cycle after a delay of 1·5 h. It is proposed that there are two 'pools' of LH in the pituitary gland of the female guinea-pig and that the second pool is 'activated' consequent upon previous hypophysial stimulation of secretion from an ovary containing adequately developed follicles.

OESTROGEN-INDUCED CHANGES IN THE SECRETION OF LUTEINIZING HORMONE CAUSED BY CONTINUOUS INFUSIONS OF LUTEINIZING HORMONE RELEASING HORMONE IN THE LONG-TERM OVARIECTOMIZED RAT

1977 ◽  
Vol 72 (2) ◽  
pp. 121-126 ◽  
Author(s):  
G. A. SCHUILING ◽  
H. P. GNODDE
Keyword(s):  
Luteinizing Hormone ◽  
Pituitary Gland ◽  
Hormone Secretion ◽  
Potential Response ◽  
Luteinizing Hormone Secretion ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Lh Rh ◽  
Induced Changes

SUMMARY Oestrogen-induced changes in luteinizing hormone secretion, caused by continuous infusions of luteinizing hormone releasing hormone (LH-RH), appear to depend on the duration of exposure of the pituitary gland to the releasing hormone. The initial oestrogen-induced depression of the potential response of the pituitary gland to LH-RH, which always seems to occur, does not necessarily turn into an enhancement of this potential response. It is suggested that this may be due to the fact that the response of the pituitary gland to LH-RH infusions is a continuously changing parameter influenced by oestrogen.

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