Priming effect of luteinizing hormone releasing hormone in the hypogonadal mouse

Fink, George; Sheward, W. J.; Charlton, H. M.

doi:10.1677/joe.0.0940283

Cited by 25 publications

(12 citation statements)

References 11 publications

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“…LH radioimmunoassay The LH content of the pituitary homogenates and samples of media were estimated in duplicate by the ovine-ovine double-antibody radioimmunoassay of Niswender, Midgley, Monroe & Reichert (1968) as used previously in our studies of LH content and release from the mouse pituitary gland (e.g. Cattanach et al 1977;Fink et al 1982;Lewis et al 1985). Samples of pituitary homogenates and incubation media were assayed in duplicate aliquots of 20 and 50 pi respectively.…”

Section: Generalmentioning

confidence: 99%

“…The priming effect of LHRH, i.e. the capacity of the decapeptide to increase the responsiveness of pituitary gonadotrophs to itself (Aiyer, Chiappa & Fink, 1974), can be elicited in both normal and hpg mice (Fink, Sheward & Charlton, 1982;Lewis, Morris & Fink, 1984). This shows that neither long-term exposure to LHRH nor a normal pituitary content of luteinizing hormone (LH) is necessary for the releasing or priming action of LHRH.…”

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confidence: 99%

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Changes in the granule population of gonadotrophs of hypogonadal (hpg) and normal female mice associated with the priming effect of LH-releasing hormone in vitro

Lewis¹,

Morris²,

Fink³

et al. 1986

Journal of Endocrinology

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Changes in the size and position of secretory granules in pituitary gonadotrophs have been studied in relationship to LH release and self-priming induced by LH-releasing hormone (LHRH) in pituitary glands from normal and hypogonadal (hpg) female mice. Hemipituitary glands were preincubated and then incubated for either 1 or 2 h in the absence or presence of LHRH (8.5 nmol/l). The glands were either processed for ultrastructural morphometry or homogenized for the determination of pituitary LH content. Morphometry was carried out on gonadotrophs identified by immunocytochemistry for LH beta using the thin/semi-thin section method. Pituitary LH content and the amount of LH released were determined by radioimmunoassay. The amount of LH released in response to the first and second hours of incubation with LHRH were similar in hpg and normal mice with a clear priming effect (three- to fourfold increase in pituitary responsiveness to LHRH) occurring in both strains. Despite a substantially reduced total number of granules (and amount of LH) in unstimulated hpg gonadotrophs, the number of granules in the outer 500 nm marginal zone of the cells was similar to that in normal mice. This could explain the similar amount of LH released from normal and hpg glands by the first LHRH challenge. The initial exposure to LHRH was also associated with a marked translocation of secretory granules from the central to the outer marginal region of cytoplasm subjacent to the gonadotroph plasmalemma, such that in 'primed' glands 60% of granules were found in this marginal zone compared with 40% (hpg) or 33% (normal) in unstimulated glands. The mean diameter of granules in the marginal zone was significantly less than that of granules in the central zone of the gonadotrophs of unstimulated glands from both normal and hpg animals. Exposure to LHRH for 1 h was associated with an increase in the number of small granules in the marginal zone and a significant decrease in the mean diameter of the gonadotroph granule population as a whole. After the primed release of LH, increased proportions of granules were still located in the marginal zone of gonadotrophs, indicating that granule migration continued during the second hour of exposure to LHRH in which primed release occurred. The primed release was associated with a detectable reduction in both the LH and granule content of gonadotrophs in normal, but not hpg glands.(ABSTRACT TRUNCATED AT 400 WORDS)

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Section: Generalmentioning

confidence: 99%

mentioning

confidence: 99%

Changes in the granule population of gonadotrophs of hypogonadal (hpg) and normal female mice associated with the priming effect of LH-releasing hormone in vitro

Lewis¹,

Morris²,

Fink³

et al. 1986

Journal of Endocrinology

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“…Studies employing injections of synthetic GnRH have previously shown that the hpg mice can respond to the hormone with a pituitary release of LH which is somewhat less than seen in normal animals (Iddon, Charlton & Fink, 1980), although the response to the priming action of GnRH on LH release was shown to be no different than normal (Fink, Sheward & Charlton, 1982). Multiple daily injections of GnRH for five days in hpg males significantly increased pituitary FSH content and testicular development (Charlton, Fink & Halpin, 1981), although seminal vesicle weights did not change during this brief period.…”

Section: Discussionmentioning

confidence: 98%

Brain Tissue Grafts in the Central Nervous System: Reversal of Hypogonadism

et al. 1983

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Transplantation of brain tissue from normal donors into the central nervous system of animals with specific central neurochemical deficiencies has been used to remedy such defects. The present studies demonstrate that the hypogonadism present in the adult male hypogonadal (hpg) mouse that is secondary to hypothalamic gonadotropin releasing hormone (GnRH) deficiency can be corrected by grafts into the anterior third ventricle of fetal preoptic area (p.o.a.) tissue. The p.o.a. is a primary site of localization of GnRH neurones in rodents. As compared with untreated hpg males, or with hpg males that had received control cortical tissue implants, the hpg animals with p.o.a. grafts showed measurable levels of GnRH within the hypothalamus. Immunocytochemical studies revealed GnRH within the transplants. Increased pituitary and plasma LH and FSH, and testicular growth with full spermatogenesis, were also evident in the hpg males that had received p.o.a. implants.

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“…The magnitude of the priming effect of LHRH was determined according to the method of Fink et al [11], Animals were anesthe tized with urethane (1.2 g/kg body weight) administered intraperitoneally as a 10% solution in 0.9% NaCI (w/v) solution. About 20 min after urethane had been injected, an initial blood sample (0.2 ml) was withdrawn from the external jugular vein and 400 ng syn thetic LHRH (Peninsula Labs Inc., Belmont, Calif.) in 0.2 ml 0.9% NaCI were injected intravenously.…”

Section: Methodsmentioning

confidence: 99%

Hyperprolactinemia Induced by Pituitary Isografts Suppresses the Priming Effect of LH-Releasing Hormone in Normal and Hypogonadal Mice

Lewis¹,

Fink²,

Dow³

et al. 1986

Neuroendocrinology

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We have investigated the effects of hyperprolactinemia, produced by pituitary isografts under the kidney capsule (16–20 days), on the LH releasing action and priming effect of LH-releasing hormone (LHRH) in normal and hypogonadal (hpg) female mice. The pituitary grafts increased the plasma prolactin concentrations about 3-fold in normal intact mice and 4-fold in hpg mice. The extent of the graft-induced hyperprolactinemia was reduced by ovariectomy in normal mice, but was the same in grafted hpg compared with intact normal mice despite the absence in the hpg mice of functioning ovaries. The priming effect of LHRH could be elicited in both types of mice by giving two injections of LHRH separated by an interval of 60 min. Hyperprolactinemia did not reduce the amount of LH released in response to a first injection of LHRH, but did reduce significantly the amount of LH released (primed) in response to a second injection of LHRH. Ovariectomy significantly increased the magnitude of the releasing action of LHRH in normal mice and prevented the graft-induced reduction of LHRH priming. These results show that hyperprolactinemia in normal and hpg mice suppresses the magnitude of the priming effect of LHRH. This may be an important mechanism by which prolactin reduces gonadotropin secretion.

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Priming effect of luteinizing hormone releasing hormone in the hypogonadal mouse

Cited by 25 publications

References 11 publications

Changes in the granule population of gonadotrophs of hypogonadal (hpg) and normal female mice associated with the priming effect of LH-releasing hormone in vitro

Changes in the granule population of gonadotrophs of hypogonadal (hpg) and normal female mice associated with the priming effect of LH-releasing hormone in vitro

Brain Tissue Grafts in the Central Nervous System: Reversal of Hypogonadism

Hyperprolactinemia Induced by Pituitary Isografts Suppresses the Priming Effect of LH-Releasing Hormone in Normal and Hypogonadal Mice

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