The role of microfilaments in the priming effect of LH-releasing hormone: an ultrastructural study using cytochalasin B

1985 ◽  
Vol 106 (2) ◽  
pp. 211-NP ◽  
Author(s):  
C. E. Lewis ◽  
J. F. Morris ◽  
G. Fink
Keyword(s):  
Adult Female ◽  
Ultrastructural Study ◽  
Incubation Medium ◽  
Priming Effect ◽  
Cytochalasin B ◽  
Secretory Granules ◽  
Releasing Hormone ◽  
Lh Releasing Hormone ◽  
Lh Secretion

ABSTRACT We have investigated the possibility that microfilaments are involved in the priming effect of LH-releasing hormone (LHRH) by ultrastructural morphometry of hemipituitary glands from adult female mice. Glands incubated for 2 consecutive hours with 8·5 nmol LHRH/1 responded with a marked increase in the amount of LH released into the medium during the second hour compared with the first hour of incubation. This priming effect of LHRH on LH secretion was accompanied by a significant margination of secretory granules and a drop in the total granule content of the gonadotrophs. Although the number of microfilaments remained the same, there was an increase in their length and a change in orientation so that the angle between the microfilaments and the plasmalemma was significantly reduced after both the first and second hour of exposure of LHRH. The addition of 14·3 μmol cytochalasin B/l to the incubation medium significantly increased the amount of LH released in the first hour of incubation when compared with the amount of LH released by LHRH alone, but completely abolished the priming effect of LHRH. Cytochalasin B also prevented the LHRH-induced increase in the length and the change in orientation of the microfilaments. These results indicate that LHRH priming involves an increase in length of microfilaments and a change in their orientation relative to the plasmalemma. J. Endocr. (1985) 106, 211–218

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

1986 ◽  
Vol 109 (1) ◽  
pp. 35-NP ◽  
Author(s):  
C. E. Lewis ◽  
J. F. Morris ◽  
G. Fink ◽  
M. Johnson
Keyword(s):  
Priming Effect ◽  
Marginal Zone ◽  
Secretory Granules ◽  
Initial Exposure ◽  
Releasing Hormone ◽  
Female Mice ◽  
Mean Diameter ◽  
Lh Release ◽  
The Mean ◽  
Lh Releasing Hormone

ABSTRACT 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 LHβ 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. The ultrastructural correlates of LH release and LHRH priming were similar in the two strains of mice, and therefore in mice neither the releasing nor the priming effect of LHRH depends upon previous exposure of the pituitary gland to LHRH or ovarian factors. The priming effect was associated with a marked shift of granules towards the plasmalemma and a decrease in granule size which most likely resulted from increased post-translational processing within secretory granules. J. Endocr. (1986) 109, 35–44

Suppression of LH secretion by oestradiol, dihydrotestosterone and trenbolone acetate in the acutely castrated bull

1984 ◽  
Vol 100 (1) ◽  
pp. 107-112 ◽  
Author(s):  
T. W. Gettys ◽  
M. J. D'Occhio ◽  
D. M. Henricks ◽  
B. D. Schanbacher
Keyword(s):  
Feedback Control ◽  
Pituitary Gland ◽  
Treated Group ◽  
Primary Site ◽  
Trenbolone Acetate ◽  
Releasing Hormone ◽  
Serum Lh ◽  
Lh Releasing Hormone ◽  
Lh Secretion

ABSTRACT Twenty acutely castrated bulls were used to investigate the role of androgenic and oestrogenic steroids in the feedback control of LH secretion. The effects of 5α-dihydrotestosterone (DHT) or the growth stimulants trenbolone acetate (TBA) or oestradiol-17β (OE2) on serum LH secretory profiles were measured. In addition, pituitary LH responses to exogenous LH releasing hormone (LHRH) were determined to differentiate between hypothalamic and pituitary sites of steroid action. At the time of castration, two groups of animals were given implants of either 45 mg OE2 or 200 mg TBA. Another group received equivalent to 30 mg daily injections of DHT. Control steers showed an increase in LH from 2·4 ± 0·5 (s.e.m.) μg/l to 7·0 ± 0·5 μg/l during the week after castration. Treatment with DHT and TBA prevented the post-castration rise in serum LH. In contrast, steers given implants of OE2 showed a significantly greater increase in LH than controls 1 day after castration, but by day 5 LH declined in the OE2-treated group to precastration values. Five weeks after castration control steers secreted LH in pulses at intervals of 40–50 min and with an amplitude of 4·2± 0·4 μg/l. Pulses were not detected in the LH profiles of the steroid-treated steers. Dihydrotestosterone and TBA significantly reduced pituitary LH responses to exogenous LHRH, whereas steers receiving OE2 showed LH responses to LHRH which were similar to those observed in castrated controls. These results support the hypothesis that androgenic and oestrogenic components participate separately in the feedback control of LH secretion in the bull. A similar LH response to exogenous LHRH in control and OE2-treated animals suggests that the primary site of oestrogen feedback is at the level of the hypothalamus. Conversely, the small LH response to LHRH in androgen-treated animals suggests that androgen feedback is, in part, imposed at the level of the pituitary gland. Interestingly, LH secretion is regulated by dosages of androgenic and oestrogenic steroids which are available commercially as growth stimulants for cattle. J. Endocr. (1984) 100, 107–112

Multiple injections of LH-releasing hormone into hypogonadal (hpg) mice induce the appearance of two morphologically distinct populations of gonadotrophs

1986 ◽  
Vol 111 (3) ◽  
pp. 483-NP ◽  
Author(s):  
C. E. Lewis ◽  
A. Megson ◽  
J. F. Morris ◽  
H. M. Charlton
Keyword(s):  
Lipid Droplets ◽  
Secretory Granules ◽  
Male And Female ◽  
Releasing Hormone ◽  
Multiple Injections ◽  
Adult Mice ◽  
Full Development ◽  
Free Cells ◽  
Pituitary Glands ◽  
Lh Releasing Hormone

ABSTRACT We have investigated the effects of multiple 2-hourly injections of LH-releasing hormone (LHRH) on the number and size of the gonadotrophs and gonadotroph secretory granules, and the lipid content of gonadotrophs in the pituitary glands of intact and gonadectomized male and female hypogonadal (hpg) mice. Gonadotrophs were identified by immunocytochemistry for LHβ, and the size and secretory status of the gonadotrophs were assessed by quantitative ultrastructural analysis of immunoidentified gonadotrophs. The administration of 60 ng LHRH by subcutaneous injection every 2 h for 15 days resulted in an increase in the number, size and granule content of LHβ-immunoidentified gonadotrophs of hpg mice to values found in normal adult mice. Large lipid droplets accumulated in 30–40% of the gonadotrophs in both male and female LHRH-treated hpg mice. Although lipid-containing gonadotrophs were larger than lipid-free cells in all LHRH-treated groups irrespective of the presence or absence of gonads, a marked difference in the number, position within the cell, and size of the secretory granules between the lipid-containing and lipid-free cells was found only in the pituitary glands of intact LHRH-treated hpg females. These results demonstrate: (a) that the effects of multiple injections of LHRH on the morphology of the gonadotrophs of hpg mice is not dependent on the presence of functioning gonads, although ovarian factors are required for the full development of morphological, and hence possibly functional, heterogeneity in the gonadotroph population in female animals, and (b) that, although multiple injections of LHRH in hpg mice are more effective than single daily injections of LHRH in stimulating pituitary-gonadal function, there is no obvious difference in the morphologically recognizable effects that these two modes of administration have on the pituitary gonadotrophs. J. Endocr. (1986) 111, 483–493

scholarly journals Effects of treatment with LH releasing hormone before the early increase in LH secretion on endocrine and reproductive development in bull calves

Reproduction ◽  
1997 ◽  
Vol 111 (1) ◽  
pp. 41-50 ◽  
Author(s):  
R. K. Chandolia ◽  
A. Honaramooz ◽  
P. M. Bartlewski ◽  
A. P. Beard ◽  
N. C. Rawlings
Keyword(s):  
Reproductive Development ◽  
Releasing Hormone ◽  
Bull Calves ◽  
Early Increase ◽  
Lh Releasing Hormone ◽  
Lh Secretion

Control of follicle-stimulating hormone secretion by steroid-free bovine follicular fluid in the ovariectomized rat

1983 ◽  
Vol 99 (1) ◽  
pp. 1-8 ◽  
Author(s):  
T. R. Koiter ◽  
G. C. J. van der Schaaf-Verdonk ◽  
H. Kuiper ◽  
N. Pols-Valkhof ◽  
G. A. Schuiling
Keyword(s):  
Luteinizing Hormone ◽  
Follicular Fluid ◽  
Hormone Secretion ◽  
Ovariectomized Rats ◽  
Ovariectomized Rat ◽  
Releasing Hormone ◽  
Basal Release ◽  
Lh Release ◽  
Lh Releasing Hormone ◽  
Lh Secretion

The effects of steroid-free bovine follicular fluid (bFF) and sodium phenobarbitone on spontaneous LH releasing hormone (LHRH)-induced secretion of FSH and LH were studied in ovariectomized rats. Luteinizing hormone releasing hormone was administered by infusion to rats anaesthetized with phenobarbitone. Bovine follicular fluid reduced FSH release and synthesis. Luteinizing hormone release remained unaffected after bFF treatment. Phenobarbitone reduced both FSH and LH release. The observed suppressive effects of bFF and phenobarbitone on FSH secretion were additive, suggesting that the basal release of FSH has an LHRH-dependent and an LHRH-independent component. Furthermore, bFF did not affect pituitary responsiveness of LH secretion to LHRH and reduced the responsiveness of FSH secretion only when administered some time before the LHRH challenge. The present observations support the view that in the ovariectomized rat the pituitary gland is the only site of action of inhibin-like activity as present in bFF.

Estradiol stimulation of LH response to LHRH and LHRH binding in pituitary cultures

1982 ◽  
Vol 242 (6) ◽  
pp. E392-E397
Author(s):  
L. K. Tang ◽  
A. C. Martellock ◽  
J. K. Horiuchi
Keyword(s):  
Cell Proliferation ◽  
Luteinizing Hormone ◽  
Priming Effect ◽  
Cultured Cells ◽  
Female Rats ◽  
Releasing Hormone ◽  
Lh Release ◽  
Estradiol Stimulation ◽  
Lh Releasing Hormone ◽  
Stimulation Of

The relationship between 17 beta-estradiol (E2) stimulation of luteinizing hormone (LH) response to LH-releasing hormone (LHRH) and E2 effect on LHRH binding was examined in pituitary monolayer cultures prepared from female rats. E2 pretreatment significantly (P less than 0.05) augmented the LHRH-induced LH release to 158-180% of the non-E2-treated controls. The maximal E2-priming effect could be observed after 1 day of treatment. E2 treatment for 3 days stimulated [D-Ala6]luteinizing hormone-releasing hormone (LHRHa) binding to about 1.5-fold that of the non-E2-treated controls without affecting the dissociation constant of LHRH receptor (Kd = 4 X 10(-10) M). The stimulatory effect of E2 on cell proliferation as determined by [3H]thymidine incorporation was also observed 3 days after treatment. However, E2 stimulation of LH accumulation in the cultured cells could be detected as early as 4 h after treatment. These results indicate that E2-priming effect on pituitary LH response to LHRH is initially associated with an increase in cellular LH content and later associated with increases in LHRH binding and in an index of cell proliferation that may include the LH-producing cells.

Pituitary receptors for LH-releasing hormone (LHRH) and responsiveness to LHRH in adult female rats after neonatal monosodium l-glutamate treatment

1985 ◽  
Vol 107 (1) ◽  
pp. 9-13 ◽  
Author(s):  
S. E. Inkster ◽  
R. N. Clayton ◽  
S. A. Whitehead
Keyword(s):  
Adult Female ◽  
Female Rats ◽  
Serum Prolactin ◽  
Female Rat ◽  
Releasing Hormone ◽  
Old Rats ◽  
Lh Releasing Hormone ◽  
Ovarian Cyclicity ◽  
Pituitary Receptors

ABSTRACT The effects of neonatal monosodium l-glutamate (MSG) treatment on pituitary responsiveness to LH-releasing hormone (LHRH) and on pituitary LHRH receptors have been investigated in the intact adult female rat. Three- to four-month-old rats treated with MSG (4 mg/g body wt) on days 2, 4, 6, 8 and 10 after birth had significantly reduced ovarian and pituitary weights, showed an absence or disruption of ovarian cyclicity after puberty, and had significantly higher concentrations of serum prolactin despite normal levels of LH. In-vitro pituitary LH responses to LHRH were in the normal range for one group of treated animals whilst in a second group the LH responses were markedly enhanced. In contrast, the total number of pituitary LHRH receptors were significantly reduced in all MSG-treated animals showing that the increased pituitary responsiveness of MSG-treated animals is not attributable to an increase in pituitary LHRH receptors. J. Endocr. (1985) 107, 9–13

Lipopolysaccharide reduces gonadotrophin-releasing hormone (GnRH) gene expression: role of RFamide-related peptide-3 and kisspeptin

2019 ◽  
Vol 31 (6) ◽  
pp. 1134 ◽  
Author(s):  
Chooi Yeng Lee ◽  
ShengYun Li ◽  
Xiao Feng Li ◽  
Daniel A. E. Stalker ◽  
Claire Cooke ◽  
...  
Keyword(s):  
Gene Expression ◽  
In Situ Hybridisation ◽  
Releasing Hormone ◽  
Related Peptide ◽  
Concomitant Reduction ◽  
Intracerebroventricular Injections ◽  
Gonadotrophin Releasing Hormone ◽  
Lh Secretion

RFamide-related peptide (RFRP)-3 reduces luteinising hormone (LH) secretion in rodents. Stress has been shown to upregulate the expression of the RFRP gene (Rfrp) with a concomitant reduction in LH secretion, but an effect on expression of the gonadotrophin-releasing hormone (GnRH) gene (Gnrh1) has not been shown. We hypothesised that lipopolysaccharide (LPS)-induced stress affects expression of Rfrp, the gene for kisspeptin (Kiss1) and/or Gnrh1, leading to suppression of LH levels in rats. Intracerebroventricular injections of RFRP-3 (0.1, 1, 5 nmol) or i.v. LPS (15μgkg−1) reduced LH levels. Doses of 1 and 5 nmol RFRP-3 were then administered to analyse gene expression by in situ hybridisation. RFRP-3 (5 nmol) had no effect on Gnrh1 or Kiss1 expression. LPS stress reduced GnRH and Kiss1 expression, without affecting Rfrp1 expression. These data indicate that LPS stress directly or indirectly reduces Gnrh1 expression, but this is unlikely to be due to a change in Rfrp1 expression.

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