Studies on the Time of Luteinizing Hormone Release in Gonadotrophin-Treated Immature Rats

Wagner, J. W.; Brown-Grant, K.

doi:10.1210/endo-76-5-958

Cited by 13 publications

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“…The timing of this release, which occurs approximately 8 h after the onset of the second period of light after the PMS injection, is dependent upon the lighting schedule to which the animals are subjected [Wagner and Brown-G rant, 1965].…”

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confidence: 99%

Pituitary and Plasma Levels of Luteinizing Hormone and Prolactin in the Immature Female Rat Following Administration of Pregnant Mares’ Serum

1975

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28-day-old female rats were killed at increasing time periods after the injection of either 30 IU pregnant mares’ serum (PMS) or saline, and pituitary and plasma luteinizing hormone (LH) and prolactin levels were measured by radioimmunoassay. Hormone concentrations were measured at intervals up to one week following injection with frequent measurements made on the afternoon preceding ovulation to better characterize and evaluate the PMS-treated immature rat as an ovulation model. Peaks in both plasma LH and prolactin occurred on the afternoon preceding ovulation. Pituitary LH was found to decrease and again increase during this afternoon period before falling to a low value on the morning following ovulation. Pituitary prolactin increased to an early afternoon maximum value, fell to a low value by late afternoon, and increased again by the morning following ovulation. Saline-treated immature female rats displayed fluctuations in plasma and pituitary LH and prolactin similar to but smaller than the afternoon changes found in PMS-treated rats. Pituitary weights were significantly greater in PMS-treated rats on the afternoon preceding ovulation. The hormonal changes encountered in the PMS-treated rat prior to ovulation appear to be similar to those encountered in the proestrous cycling female rat, although more study is necessary to validate this system as a model of spontaneous ovulation in the adult animal. The data suggest that PMS causes ovulation in immature rats by amplifying or synchronizing existing hormonal rhythms.

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confidence: 99%

Pituitary and Plasma Levels of Luteinizing Hormone and Prolactin in the Immature Female Rat Following Administration of Pregnant Mares’ Serum

1975

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“…Thus, the increase in eCG dosage can be expected to enlarge the size of the ovulable follicular pool. However, during folliculogenesis, excessive follicular growth due to the eCG treatment is reported to cause an endogenous LH release, which in turn induces partial ovulation and/or atretic changes in growing follicles before the hCG treatment [3,4]. In adult rats, pentobarbital anesthesia during an appropriate period between eCG and hCG treatments is reported to increase the number of ova shed, probably by its blockage of the endogenous LH release [5].…”

Section: Superovulationmentioning

confidence: 99%

Induction of Superovulation in Acutely Hypophysectomized Rats and Presence of Ovulable Population of Follicles.

Sakai

Takahashi

1993

Journal of Reproduction and Development

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Abstract. Superovulation was induced in intact and acutely hypophysectomized mature rats by a successive eCG-hCG treatment.In the rats hypophysectomized after the onset of GTH surges, increment in eCG dosages maximized the number of ova shed by the following hCG treatment, and the maximum number was similar to those in non-hypophysectomized rats. In the rats hypophysectomized before GTH surges, however, the number of ova shed was significantly less, but this decrease was restored by an hCG injection immediately after the hypophysectomy. These results indicate that the maximum number of ova shed is determined by the limited number of eCG-responsive follicles that are generated during exposure to an antecedent LH surge. In intact rats, excess doses of eCG elicited enhanced progesterone secretion which, in turn, established PRL surges. These PRL surges appears to cause atretic changes in growing follicles and decreased the number of ova shed by the following hCG treatment. Thus, the upper limit of the number of ova shed in mature cycling rats subjected to the eCG-hCG treatment was estimated to be approximately 80.

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“…Detailed studies have led to the view that ovulation itself depends upon the LH surge on the second day afternoon following PMS administration Meyer, 1962, 1963;Strauss and Meyer, 1962;Zarrow and Quinn, 1963;Quinn and Zarrow, 1964;Wagner and Brown-Grant, 1965;Klawon et al, 1971) and endogenous gonadotropin requirements for follicular development have been clarified (Sasamoto and Kennan, 1973). The second estrus, however, was observed about 9 days after the first ovulation in these rats (Hashimoto and Wiest, 1969; Taya et al, in press), and little is known about the follicular development after PMS-induced ovulation in immature rats.…”

Section: Synopsismentioning

confidence: 99%

Follicular Development after the First Ovulation in Immature Rats Pretreated with PMS

Sawamoto

Sasamoto

1973

Endocrinol Japon

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SynopsisA single injection of PMS induces ovulation in immature rats on the third day morning after the treatment. The second estrus occurred 9 days after the first ovulation. Follicles of the succeeding cycle developed the capacity to ovulate 3 days after the first ovulation in 3 out of 5 rats, but could not be maintained in an ovulable state during the next 24 hr.When supplementary PMS was given just after the first LH surge, follicles developed the capacity to ovulate within 1.5 days after the first ovulation and the second ovulation occurred in 7 out of 10 on the fourth day morning after the first ovulation. Vaginal smears showed a 4-day-cyclic pattern in these animals after supplementary PMS administration.From these experiments, it is concluded that immature rats pretreated with PMS were in an anestrous state during 8 days after the first ovulation, not due to the activation of corpora lutea, but due to the failure of follicular development. Plasma levels of gonadotropin responsible for follicular growth and maintenance after the first ovulation were discussed.A single injection of PMS produces ovulation in immature rats on the third day morning after the treatment. Detailed studies have led to the view that ovulation itself depends upon the LH surge on the second day afternoon following PMS administration Meyer, 1962, 1963;Strauss and Meyer, 1962;Zarrow and Quinn, 1963;Quinn and Zarrow, 1964;Wagner and Brown-Grant, 1965;Klawon et al., 1971) and endogenous gonadotropin requirements for follicular development have been clarified (Sasamoto and Kennan, 1973). The second estrus, however, was observed about 9 days after the first ovulation in these rats (Hashimoto and Wiest, 1969; Taya et al., in press), and little is known about the follicular development after PMS-induced ovulation in immature rats.The present experiments are concerned with the follicular development of the succeeding cycle after the first ovulation in immature rats pretreated with PMS. Materials and MethodsThe rats were of the Wistar strain bred in the laboratory and aged 25 days old (day 25) at the start of the experiments. The animals were housed in an air-conditioned room illuminated from 5.00 to 19.00 hr throughout the experiments.Three IU of PMS was administered subcutaneously on day 25 between 9.00 to 10.00 hr. Vaginal smears were taken daily after vaginal opening. Follicular responsiveness to HCG after the first ovulationIn order to examine the follicular development following the first ovulation in immature rats pretreated with 3 IU of PMS, 10 IU of HCG was singly

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Studies on the Time of Luteinizing Hormone Release in Gonadotrophin-Treated Immature Rats

Cited by 13 publications

References 0 publications

Pituitary and Plasma Levels of Luteinizing Hormone and Prolactin in the Immature Female Rat Following Administration of Pregnant Mares’ Serum

Pituitary and Plasma Levels of Luteinizing Hormone and Prolactin in the Immature Female Rat Following Administration of Pregnant Mares’ Serum

Induction of Superovulation in Acutely Hypophysectomized Rats and Presence of Ovulable Population of Follicles.

Follicular Development after the First Ovulation in Immature Rats Pretreated with PMS

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