OESTRADIOL-17α AND PITUITARY RESPONSIVENESS TO LUTEINIZING HORMONE RELEASING FACTOR IN THE RAT: A STUDY USING RECTANGULAR PULSES OF OESTRADIOL-17β MONITORED BY NON-CHROMATOGRAPHIC RADIOIMMUNOASSAY

1977 ◽  
Vol 73 (3) ◽  
pp. 441-453 ◽  
Author(s):  
S. R. HENDERSON ◽  
CHRISTINE BAKER ◽  
G. FINK
Keyword(s):  
Luteinizing Hormone ◽  
Priming Effect ◽  
Plasma Concentrations ◽  
Oestrous Cycle ◽  
Facilitatory Effect ◽  
Oestradiol Benzoate ◽  
High Doses ◽  
Plasma Oestradiol

SUMMARY Plasma concentrations of oestradiol-17β were measured by a non-chromatographic radioimmunoassay during the oestrous cycle, after the s.c. injection of 2·5 or 10 pg oestradiol benzoate (OB), or the s.c. implantation of Silastic capsules containing crystalline oestradiol-17β. The profile of endogenous plasma oestradiol-17β concentrations was similar to that reported by other workers, and lay between the concentrations produced by the low and high doses of OB. The rectangular pulses of increased plasma oestradiol concentrations, produced during the period of implantation of the Silastic capsules, were used to determine the time taken for oestradiol-17β to exert its facilitatory effect on the gonadotrophin response to LH-releasing factor (RF). In animals ovariectomized at dioestrus, oestradiol, at concentrations similar to those reached during the peak of the spontaneous surge, first reduced the LH response. However, after 7 h, responsiveness increased significantly to reach a peak at 12 h. The FSH response was also greatest 12 h after ovariectomy. In animals ovariectomized at metoestrus the effect of oestradiol on the LH response was significantly less than in rats ovariectomized at dioestrus, and the FSH responses were lower than those in animals bearing empty capsules and examined at the same time after ovariectomy. These findings together with the effects of long-term exposure to sodium pentobarbitone are considered with respect to the possible mechanisms, including the priming effect of LH-RF, which may produce increased pituitary responsiveness after ovariectomy and exposure to oestrogen.

A PRIMING EFFECT OF LUTEINIZING HORMONE RELEASING FACTOR ON THE ANTERIOR PITUITARY GLAND IN THE FEMALE RAT

1974 ◽  
Vol 62 (3) ◽  
pp. 573-588 ◽  
Author(s):  
M. S. AIYER ◽  
SHARON A. CHIAPPA ◽  
G. FINK
Keyword(s):  
Luteinizing Hormone ◽  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Priming Effect ◽  
Plasma Concentrations ◽  
External Jugular Vein ◽  
Anterior Pituitary Gland ◽  
Female Rat ◽  
Oestradiol Benzoate ◽  
Plasma Oestradiol

SUMMARY The possibility that luteinizing hormone releasing factor (LH-RF) not only stimulates the secretion of luteinizing hormone (LH) but also has the ability to prime the anterior pituitary gland so that further exposure to LH-RF enhances the responsiveness of the gonadotrophs has been investigated. The effect of two successive i.v. injections of the same dose of LH-RF (50 ng/100 g body weight) on the concentration of LH in plasma was determined in rats anaesthetized with sodium pentobarbitone. Blood samples were collected from the external jugular vein immediately before and at frequent intervals after the injections of LH-RF, and plasma concentrations of LH and, in some samples, follicle-stimulating hormone (FSH) were measured by radioimmunoassay. In rats anaesthetized with sodium pentobarbitone at 13.30 h of pro-oestrus and injected i.v. with two successive doses of LH-RF, separated by an interval of 30, 60, 120 or 240 min, the LH response to the second injection was significantly greater than that to the first. The LH response was greatest when the two doses were separated by an interval of 60 min. The FSH response to the second injection of LH-RF given 60 min after the first was not significantly different from that to the first injection. Compared with pro-oestrus, the priming effect of LH-RF was much less at metoestrus and dioestrus, and could not be demonstrated at oestrus. Ovariectomy on the morning of dioestrus reduced the LH responses to the first and second injections of LH-RF given 60 min apart on the afternoon of pro-oestrus, an effect which was partially reversed by administration of oestradiol benzoate shortly after ovariectomy. These findings together with the fact that administration of oestradiol benzoate at metoestrus increased the magnitude of the priming effect of LH-RF at dioestrus suggest that the response at pro-oestrus is dependent upon the rise in plasma oestradiol-17β which reaches a peak on the morning of pro-oestrus. Although oestrogen plays an important role in determining the magnitude of the priming effect of LH-RF, it appears that none of the steroids secreted by either the ovaries or the adrenal glands mediates this effect since the profile and magnitude of the LH responses to the two doses of LH-RF injected at pro-oestrus into rats adrenalectomized and ovariectomized before the first injection of LH-RF were comparable to those in control animals. The possible role which the priming effect of LH-RF may play in the development of the preovulatory surge of LH in the rat and man is discussed.

PLASMA AND PITUITARY LUTEINIZING HORMONE AND PERIPHERAL PLASMA OESTRADIOL CONCENTRATIONS IN THE NORMAL OESTROUS CYCLE OF THE RAT AND AFTER EXPERIMENTAL MANIPULATION OF THE CYCLE

1972 ◽  
Vol 53 (1) ◽  
pp. 17-30 ◽  
Author(s):  
F. NAFTOLIN ◽  
K. BROWN-GRANT ◽  
C. S. CORKER
Keyword(s):  
Luteinizing Hormone ◽  
Plasma Levels ◽  
Experimental Manipulation ◽  
Oestrous Cycle ◽  
Postnatal Life ◽  
Normal Cycle ◽  
Rapid Fall ◽  
Major Increase ◽  
Plasma Oestradiol

SUMMARY Plasma and pituitary luteinizing hormone (LH) concentrations were measured by radioimmunoassay at different stages of the normal 4- and 5-day oestrous cycle of rats. Plasma levels were low except between the afternoon of pro-oestrus and the morning of oestrus when levels were high but variable. Pituitary LH content and concentration were less consistent but averaged values showed a steady rise from a low level after ovulation to a peak on the afternoon of pro-oestrus, and a rapid fall that evening when plasma levels rose rapidly. No significant differences were observed in plasma LH between 4- and 5-day cycles; in particular there was no reduction at metoestrus or dioestrus-1 or increase on the evening of dioestrus-2. Plasma oestradiol was already high on the morning of dioestrus-2 in some rats and in all rats by that evening. On the morning of pro-oestrus in the 5-day cycle, plasma oestradiol was still high but somewhat lower than at the corresponding stage in the 4-day cycle. Blocking ovulation by administration of sodium pentobarbitone at prooestrus in a 4-day cycle prevented the rise in plasma LH and the fall in pituitary content. Blocking generally failed in animals whose plasma LH had reached the level of 20 ng/ml or more at the time of injection. Plasma oestradiol levels on the morning of the expected day of oestrus were higher than normal in animals in which ovulation was blocked by pentobarbitone but were below pro-oestrous values. In the anovulatory state induced by exposure to constant light no major increase in plasma LH was detected after 24 days of illumination or after 3 months exposure. Animals rendered anovulatory by injection of testosterone propionate on the 4th day of postnatal life had low plasma LH levels as adults. All three groups had a low pituitary LH content. The animals exposed to long-term light and those treated with androgen generally had plasma oestradiol concentrations below the peak levels seen on the morning of pro-oestrus in the normal cycle.

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.

scholarly journals Effects of Oestradiol on Plasma Concentrations of Luteinizing Hormone in Ovariectomized Ewes with Clover Disease

1983 ◽  
Vol 36 (3) ◽  
pp. 295 ◽  
Author(s):  
NR Adams ◽  
GB Martin
Keyword(s):  
Luteinizing Hormone ◽  
Breeding Season ◽  
Intravenous Injection ◽  
Intramuscular Injection ◽  
Prolonged Exposure ◽  
Plasma Concentrations ◽  
Oestradiol Benzoate ◽  
Baseline Levels ◽  
The Difference ◽  
Clover Pasture

The effects of oestradiol on plasma luteinizing hormone (LH) concentrations were examined in 15 ovariectomized control ewes and 15 similar ewes with permanent infertility after prolonged grazing on oestrogenic clover pasture ('clover disease'). Before treatment, the plasma concentrations of LH were similar in the control and affected ewes. After intravenous injection with 40 pg oestradiol-I 7 p during the anoestrous season, the decline in LH concentration was greater in the clover-affected ewes and the subsequent elevation above original baseline levels was smaller. After intramuscular injection with 15 or 30 pg oestradiol benzoate during the normal breeding season, fewer clover-affected ewes showed a surge of LH, and the response was both reduced and retarded. This difference between the two groups has not been observed in studies on intact ewes, and it is suggested that in intact ewes the difference is masked by a greater tonic LH activity in affected ewes. The results of the present study are consistent with the hypothesis that prolonged exposure to oestrogenic pasture has a differentiating, or 'androgenizing' effect on the adult ewe.

PLASMA AND PITUITARY LUTEINIZING HORMONE CONCENTRATIONS AND PERIPHERAL PLASMA OESTRADIOL CONCENTRATION DURING EARLY PREGNANCY AND AFTER THE ADMINISTRATION OF PROGESTATIONAL STEROIDS IN THE RAT

1972 ◽  
Vol 53 (1) ◽  
pp. 31-35 ◽  
Author(s):  
K. BROWN-GRANT ◽  
C. S. CORKER ◽  
F. NAFTOLIN
Keyword(s):  
Luteinizing Hormone ◽  
Marked Decrease ◽  
Single Injection ◽  
Normal Pregnancy ◽  
Oestrous Cycle ◽  
Pregnant Rats ◽  
Pregnant Rat ◽  
Peripheral Plasma ◽  
Blastocyst Implantation ◽  
Plasma Oestradiol

SUMMARY Plasma luteinizing hormone (LH) concentrations were already lower on Day 2 of pregnancy than at the same time after the preceding ovulation in the non-pregnant rat, and fell progressively up to Day 16 of pregnancy. No evidence was obtained of any increase at the time when the ovulatory surge of LH would have occurred if the animal had not become pregnant. Pituitary LH concentration was lower in mated rats on the morning of Day 0 of pregnancy than in unmated controls on the morning of the day of oestrus. Subsequently it increased slowly to reach a level higher than at any stage of the oestrous cycle by Day 8 of pregnancy and remained high until at least Day 16 of pregnancy. Peripheral plasma oestradiol concentration increased late on Day 2 of pregnancy and was still raised on Day 4 but was never more than about one fourth of the peak concentration seen on the morning of prooestrus during the oestrous cycle. There were similar changes in plasma LH and oestradiol concentrations in the 48 h after a single injection of 2·5mg progesterone on the morning of the day of dioestrus, a procedure that delays ovulation by 1 or 2 days. Administration of a synthetic progestational compound (medroxyprogesterone acetate) to pregnant rats delayed blastocyst implantation and the delay was associated with a marked decrease in peripheral plasma LH to levels below those of normal pregnancy.

scholarly journals Secretion of inhibin A, inhibin B and inhibin pro-alphaC during the oestrous cycle of the golden hamster (Mesocricetus auratus)

1999 ◽  
Vol 162 (3) ◽  
pp. 451-456 ◽  
Author(s):  
K Ohshima ◽  
H Kishi ◽  
M Itoh ◽  
G Watanabe ◽  
K Arai ◽  
...  
Keyword(s):  
Golden Hamster ◽  
Plasma Concentrations ◽  
Follicular Development ◽  
Early Morning ◽  
Oestrous Cycle ◽  
Inhibin B ◽  
Enzyme Linked Immunosorbent Assay ◽  
Inhibin A ◽  
Negative Relationships ◽  
Plasma Oestradiol

Plasma concentrations of inhibin pro-alphaC, inhibin A and inhibin B were determined by enzyme-linked immunosorbent assay at 6 h intervals throughout the 4-day oestrous cycle of the golden hamster. Plasma concentrations of follicle-stimulating hormone (FSH) and oestradiol-17beta were also measured by radioimmunoassay during the oestrous cycle. Plasma concentrations of inhibin A increased from the early morning of day 1 (day 1=day of ovulation) and reached plateau levels at 0500 h on day 2. An abrupt increase in plasma concentrations of inhibin A was found at 1700 h on day 4, when the preovulatory FSH surge was observed. An increase in plasma concentrations of inhibin B occurred on day 1 and reached plateau levels at 1700 h on day 1. The levels remained elevated until 0500 h on day 4 and declined gradually by 2300 h on day 4. Plasma concentrations of inhibin pro-alphaC gradually increased with some fluctuation from day 1 to 1700 h on day 4 and then declined. Significant negative relationships were noted between plasma FSH and both dimeric forms of inhibin from day 1 to day 3. Significant positive relationships were found between plasma oestradiol-17beta and inhibin A or inhibin pro-alphaC throughout the oestrous cycle. In contrast, no significant relationship was found between plasma oestradiol-17beta and inhibin B. These findings suggest that both dimeric forms of inhibin play a role in the regulation of FSH secretion during follicular development. These findings also suggest that inhibin pro-alphaC could be secreted primarily by large follicles, and early atretic follicles could also be responsible for inhibin pro-alphaC secretion. On the other hand, the secretory pattern of dimeric inhibins might shift from inhibin B to inhibin A with follicular development.

RELEASE OF GONADOTROPHIN IN OVARIECTOMIZED MICE AFTER EXPOSURE TO MALES

1969 ◽  
Vol 44 (3) ◽  
pp. 293-297 ◽  
Author(s):  
F. H. BRONSON ◽  
C. DESJARDINS
Keyword(s):  
Luteinizing Hormone ◽  
Follicle Stimulating Hormone ◽  
Plasma Concentrations ◽  
Neural Pathway ◽  
Ovariectomized Mice ◽  
Oestradiol Benzoate ◽  
Stimulating Hormone

SUMMARY Gonadectomized female C57BL/6J mice were caged with males to determine the effect of male stimuli on release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Concentrations of hypophysial and plasma FSH were significantly higher after 3 days of exposure to males when compared with controls maintained in the absence of a male. Hypophysial and plasma concentrations of LH were also higher in females caged with males, but not significantly so. Ovariectomized females were given 0·01 μg. oestradiol benzoate daily for 4 days in a second experiment and the effect of cohabitation re-evaluated. There were no significant effects of exposure to males on either FSH or LH after the oestradiol injections. Therefore the presence of males enhances synthesis and release of FSH in gonadectomized females. In addition, the results of the second experiment suggest that oestrogen interferes with this response in some way, possibly blocking the neural pathway utilized by male stimuli.

Plasma oestradiol, progesterone and luteinizing hormone concentrations during the ovine oestrous cycle

Reproduction ◽  
1972 ◽  
Vol 31 (3) ◽  
pp. 501-a-501 ◽  
Author(s):  
H. Pant ◽  
C Hopkinson ◽  
R. Fitzpatrick
Keyword(s):  
Luteinizing Hormone ◽  
Oestrous Cycle ◽  
Plasma Oestradiol

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.

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