Influence of dietary intake and weight variation on LH release after a gonadotrophin-releasing hormone (GnRH) injection during the post-partum period of the nursing cow

ABSTRACT Cyproterone acetate (100–150 mg daily) was administered to 8 male patients with excessive libido. Within 3 months a significant fall (P < 0.02) in plasma testosterone was demonstrated. The plasma luteinising hormone (LH) and follicle stimulating hormone (FSH) responses to gonadotrophin releasing hormone (LH/FSH-RH) were also significantly impaired (P < 0.05). A direct correlation between the resting plasma testosterone level and the LH response to LH/FSH-RH was demonstrated (r = 0.743). It is concluded that the fall in plasma testosterone levels in patients receiving cyproterone acetate may be attributed to suppression of LH release, rather than an antiandrogen effect on the testis or hypothalamus.

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Effect of basal and pulsatile LH release on FSH-stimulated follicle growth in ewes chronically treated with gonadotrophin-releasing hormone agonist

Journal of Endocrinology ◽

10.1677/joe.0.1280449 ◽

1991 ◽

Vol 128 (3) ◽

pp. 449-456 ◽

Cited By ~ 9

Author(s):

H. M. Picton ◽

A. S. McNeilly

Keyword(s):

Gnrh Agonist ◽

Follicular Development ◽

Follicle Growth ◽

Releasing Hormone ◽

Normal Number ◽

Stage Of Development ◽

Normal Diameter ◽

Lh Release ◽

Gonadotrophin Releasing Hormone ◽

Follicular Response

ABSTRACT Ewes chronically treated with gonadotrophin-releasing hormone (GnRH) agonist were used to investigate the importance of the peripheral concentration of LH in FSH-stimulated follicular development. Twenty-four Welsh Mountain ewes were treated with two agonist implants containing 3·3 mg buserelin. During week 6 of treatment all the ewes were given a 72-h continuous infusion of ovine FSH alone (3 μg/h) or FSH with large (7·5 μg)- or small (2·5 μg) amplitude pulses of ovine LH delivered at 4-hourly intervals. The importance of baseline LH throughout the FSH infusion was evaluated in six animals which were treated with a specific antiserum against bovine LH (LH-AS) 15–20 h before the start of FSH treatment. In the absence of LH-AS, infusion of FSH alone or with large or small pulses of LH stimulated the development of a normal number of small follicles (≤ 2·5 mm in diameter) and large follicles (> 2·5 mm in diameter). These follicles had normal diameter and steroid secretion compared with control ewes on day 8 of the luteal phase. In contrast, the animals pretreated with LH-AS developed no follicles > 2·0 mm in diameter but the number of small follicles per ewe was significantly (P < 0·05) increased. These results support the hypothesis that FSH in the absence of pulsatile LH release stimulates preovulatory follicular development in ewes treated with GnRH agonist. The follicular response to LH pulses of different amplitude is dependent on both the stage of development of the follicle and the peripheral concentration of FSH. The endogenous basal level of LH present throughout the FSH infusion is essential for FSH to induce follicle growth beyond > 2·5 mm in diameter. Journal of Endocrinology (1991) 128, 449–456

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Effects of crude and highly purified bovine inhibin (Mr 32 000 form) on gonadotrophin production by ovine pituitary cells in vitro: inhibin enhances gonadotrophin-releasing hormone-induced release of LH

Journal of Endocrinology ◽

10.1677/joe.0.1270149 ◽

1990 ◽

Vol 127 (1) ◽

pp. 149-159 ◽

Cited By ~ 11

Author(s):

S. Muttukrishna ◽

P. G. Knight

Keyword(s):

Primary Cultures ◽

Suppressive Effect ◽

Pituitary Cells ◽

Dependent Manner ◽

Α Subunit ◽

Releasing Hormone ◽

Lh Release ◽

Gonadotrophin Releasing Hormone

ABSTRACT Primary cultures of ovine pituitary cells (from adult ewes) were used to investigate the actions of steroid-free bovine follicular fluid (bFF) and highly-purified Mr 32 000 bovine inhibin on basal and gonadotrophin-releasing hormone (GnRH)-induced release of FSH and LH. Residual cellular contents of each hormone were also determined allowing total gonadotrophin content/well to be calculated. As in rats, both crude and highly purified inhibin preparations promoted a dose (P < 0·001)- and time (P < 0·001)-dependent suppression of basal and GnRH-induced release of FSH as well as an inhibition of FSH synthesis, reflected by a fall in total FSH content/well. However, while neither inhibin preparation affected basal release of LH or total LH content/well, GnRH-induced LH release was significantly (P< 0·001) increased by the presence of either bFF (+ 75%) or highly-purified inhibin (+ 64%) in a dose- and time-dependent manner. This unexpected action of bFF on GnRH-induced LH release was abolished in the presence of 5 μl specific anti-inhibin serum, confirming that the response was indeed mediated by inhibin. Furthermore, neither oestradiol-17β (1 pmol/l–10 nmol/l) nor monomeric α-subunit of bovine inhibin (2·5–40 ng/ml) significantly affected basal or GnRH-induced release of LH. These in-vitro findings for the ewe lend support to a number of recent in-vivo observations and indicate that, in addition to its well-documented suppressive effect on the synthesis and secretion of FSH, inhibin may actually facilitate LH release in this species, in marked contrast to its action in the rat. Journal of Endocrinology (1990) 127, 149–159

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Interaction of endogenous chicken gonadotrophin-releasing hormone-I and -II on chicken pituitary cells

Journal of Endocrinology ◽

10.1677/joe.0.1170043 ◽

1988 ◽

Vol 117 (1) ◽

pp. 43-49 ◽

Cited By ~ 14

Author(s):

J. A. King ◽

J. S. Davidson ◽

R. P. Millar

Keyword(s):

Gnrh Receptor ◽

Receptor Type ◽

Single Type ◽

Receptor Subtypes ◽

Pituitary Cells ◽

Gnrh Antagonists ◽

Single Class ◽

Releasing Hormone ◽

Lh Release ◽

Gonadotrophin Releasing Hormone

ABSTRACT The presence of two endogenous forms of gonadotrophin-releasing hormone (GnRH) in the chicken hypothalamus (chicken GnRH-I ([Gln8]GnRH) and chicken GnRH-II ([His5,Trp7,Tyr8]GnRH)), and the stimulation of gonadotrophins by both forms, suggests the possible existence of GnRH receptor subtypes and gonadotroph subtypes in the chicken pituitary. This question was investigated by assessing the effects of various combinations of the two known forms of chicken hypothalamic GnRH and antagonist analogues of GnRH on LH release from dispersed chicken anterior pituitary cells in both static and perifused systems. The relative inhibition of chicken GnRH-I-stimulated and chicken GnRH-II-stimulated LH release by 12 GnRH antagonists did not differ significantly, suggesting a single GnRH receptor type. Chicken GnRH-II was approximately sixfold more potent than chicken GnRH-I in releasing LH. Release of LH in response to maximal doses of chicken GnRH-I and chicken GnRH-II and to a mixture of both was similar and the two peptides were not additive in their effects, consistent with the presence of a single type of LH gonadotroph and a GnRH receptor which binds both forms of GnRH. Each form of GnRH desensitized cells to subsequent stimulation with the other form, providing additional evidence for a single type of LH gonadotroph. These findings suggest that chicken GnRH-I and -II stimulate gonadotrophin release through a single GnRH receptor type on a single class of LH gonadotroph in the chicken pituitary. J. Endocr. (1988) 117,43–49

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Influence of the characteristics of pulses of gonadotrophin releasing hormone on the dynamics of luteinizing hormone release from perifused sheep pituitary cells

Journal of Endocrinology ◽

10.1677/joe.0.0980411 ◽

1983 ◽

Vol 98 (3) ◽

pp. 411-421 ◽

Cited By ~ 33

Author(s):

R. P. McIntosh ◽

J. E. A. McIntosh

Keyword(s):

Luteinizing Hormone ◽

Anterior Pituitary ◽

Pulse Width ◽

Pulse Amplitude ◽

Threshold Value ◽

Pituitary Cells ◽

Hormone Release ◽

Releasing Hormone ◽

Lh Release ◽

Gonadotrophin Releasing Hormone

The effects were studied of varying the frequency, width and amplitude of pulses of gonadotrophin releasing hormone (GnRH) on the release of LH from anterior pituitary cells. Dispersed sheep cells supported in Sephadex were perifused with medium for 10 h and stimulated with different constant pulse patterns of GnRH. The timing of release of LH was measured by radioimmunoassay of the effluent fractions. Pulses of GnRH ranging in duration from 2 min every 8 min to 16 min every 128 min, and in concentration from 1·7 pmol/l to 250 nmol/l were applied to the cells, as well as continuous stimulation. Comparisons of differences between LH release patterns among samples of the same preparation of cells were used to demonstrate the effects of different GnRH stimulatory regimes. It was concluded that (1) the frequency of GnRH stimulation was important to the nature of LH release (periods shorter than about 16 min between pulses reduced LH output and caused faster desensitization of response), (2) the pulse width of GnRH input was important (the rising edge of the pulse produced greater LH output per unit of GnRH input than did continued application of GnRH within a pulse and wider pulses combined with shorter periods reduced LH output) and (3) over a threshold value of 5–10 nmol GnRH/1 pulse amplitude had little further influence on LH output or rate of desensitization in dispersed cells. These findings reinforce the hypothesis that the rising edge of the GnRH pulse is the major stimulant to LH release.

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Gonadotrophin–releasing hormone administered in continuous low dose can induce ovulation and normal corpora lutea in acyclic post–partum ewes and seasonally anoestrous ewes

Australian Veterinary Journal ◽

10.1111/j.1751-0813.1994.tb03354.x ◽

1994 ◽

Vol 71 (4) ◽

pp. 123-125 ◽

Cited By ~ 1

Author(s):

PJ WRIGHT ◽

AH WILLIAMS ◽

IJ CLARKE

Keyword(s):

Low Dose ◽

Post Partum ◽

Corpora Lutea ◽

Releasing Hormone ◽

Gonadotrophin Releasing Hormone

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Effects of 31 kDa bovine inhibin on FSH and LH in rat pituitary cells in vitro: antagonism of gonadotrophin-releasing hormone agonists

Journal of Endocrinology ◽

10.1677/joe.0.1190233 ◽

1988 ◽

Vol 119 (2) ◽

pp. 233-241 ◽

Cited By ~ 27

Author(s):

P. G. Farnworth ◽

D. M. Robertson ◽

D. M. de Kretser ◽

H. G. Burger

Keyword(s):

Pituitary Cells ◽

Sprague Dawley ◽

Releasing Hormone ◽

Pretreatment Period ◽

Lh Release ◽

Gonadotrophin Releasing Hormone ◽

Constitutive Synthesis ◽

Rat Pituitary Cells ◽

Median Effective Concentration

ABSTRACT The effects of 31 kDa bovine inhibin on the release of FSH and LH stimulated by gonadotrophin-releasing hormone (GnRH) or its agonist analogue buserelin have been studied using 5-day-old cultures of pituitary cells prepared from adult male Sprague–Dawley rats. Exposure of cultures to increasing concentrations of inhibin for 3 days before and during a 4-h stimulation with GnRH resulted in the progressive suppression of both basal and stimulated gonadotrophin release. At the highest inhibin concentrations FSH release was abolished (inhibin median inhibitory concentration (IC50) = 0·15 U/ml) whereas LH release was suppressed by 75% (IC50 = 0·93 U/ml). To correct for the reduced size of the FSH pool resulting from inhibin pretreatment, the amount of FSH or LH released by an agonist was expressed as a proportion of the total hormone available for release in each case. Following this adjustment, concentrations of inhibin producing maximal effects increased the GnRH median effective concentration for FSH release 4·1-fold and that for LH release 2·2-fold, with inhibin IC50 values of 0·45 and 0·32 U/ml respectively. Inhibin also suppressed the maximum proportion of both FSH and LH that excess GnRH released in 4 h by 36%, with IC50 values of 0·53 and 0·76 U/ml respectively. These effects were not changed by reduction of the inhibin pretreatment period from 3 days to 1 day or by exclusion of inhibin during the stimulation period. After a 3-day pretreatment, inhibin inhibited gonadotrophin release by buserelin less effectively than that by GnRH, but the pattern of antagonism was the same. The results show that purified bovine inhibin antagonizes the release of both FSH and LH stimulated by either GnRH or buserelin in vitro by reducing the apparent potency of GnRH agonists and by decreasing the proportion of total available gonadotrophin that can be released by an excess of GnRH agonist. Higher concentrations of inhibin are required for these common actions against stimulated release of FSH and LH than for the inhibition of FSH tonic synthesis/basal release, indicating one or more secondary sites of inhibin action in addition to its primary selective action to suppress the constitutive synthesis of FSH. J. Endocr. (1988) 119, 233–241

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OESTRADIOL RECEPTORS IN THE RAT ANTERIOR PITUITARY GLAND DURING THE OESTROUS CYCLE: QUANTITATION OF RECEPTOR ACTIVITY IN RELATION TO GONADOTROPHIN RELEASING HORMONE-MEDIATED LUTEINIZING HORMONE RELEASE

Journal of Endocrinology ◽

10.1677/joe.0.0760211 ◽

1978 ◽

Vol 76 (2) ◽

pp. 211-218 ◽

Cited By ~ 11

Author(s):

K. K. SEN ◽

K. M. J. MENON

Keyword(s):

Pituitary Gland ◽

Binding Sites ◽

Anterior Pituitary ◽

Anterior Pituitary Gland ◽

Oestrous Cycle ◽

Hormone Release ◽

Releasing Hormone ◽

Lh Release ◽

Gonadotrophin Releasing Hormone ◽

Stimulation Of

Specific oestradiol binding to a receptor in nuclear and cytosol fractions of the rat anterior pituitary gland and pituitary responsiveness to gonadotrophin releasing hormone (GnRH) during the oestrous cycle have been studied. To accomplish this, both unoccupied and occupied oestradiol-binding sites in the cytosol and oestradiol-binding sites in the nucleus and total cell were measured during the oestrous cycle. The concentration of unoccupied and occupied sites and total oestradiol binding in the cytosol fluctuated during the cycle. At pro-oestrus, the concentration of cytosol receptor was diminished by about 40% and replenishment occurred during oestrus. On the other hand, a profound increase in concentrations of cellular and nuclear receptors occurred at pro-oestrus. Administration of GnRH significantly stimulated LH release at all stages of the cycle. The maximum stimulation of LH release by GnRH was observed at 13.00 h of pro-oestrus. From these studies, it is concluded that pituitary responsiveness to exogenous GnRH during pro-oestrus parallels the changes in the content of oestrogen receptors in the cytosol and nucleus.

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