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PubMed1975

Anti-luteinizing (LH)-releasing activity of several analogues of LH-releasing hormone.

The anti-LH-releasing activity of several analogues of LH-RH was tested by 2-hour infusion in ovariectomized, estrogen-progesterone-pretreated rats and in immature male rats. [Leu3]LH-RH, [Leu3, desGly10]-LH-RH ethylamide, [desHis2, Leu3,desGly10]-LH-RH ethylamide, [Gly2, Leu3,desGly10]-LH-RH ethylamide, [Leu1, desGly10]-LH-RH ethylamides, [desHis2,D-Ala6,desGly10]-LH-RH ethylamide, [desHis2,Leu3,D-Ala6, desGly10]-LH-RH ethylamide, and [D-pGlu1,desGly10]-LH-RH ethylamide, and and [D-pGlu1,desHis2,desGly10]-LH-RH ethylamide showed some anti-LH-releasing activity, but never completely inhibited the increase in serum LH in response to LH-RH. No significant differences were found among the analogues tested and [desHis2,desGly10]-LH-RH ethylamide, and inhibitory potency was not improved with those peptides containing D-alanine in position 6 of the chain. None of the analogues tested, including [desHis2,desGly10]-LH-RH ethylamide, was able to block the LH-RH-induced FSH release in these systems.

Animals↗
PubMed1984

Deglycosylated luteinizing hormone (LH) prevents desensitization of cyclic adenosine monophosphate response by LH: dissociation between receptor uncoupling and down-regulation.

Deglycosylated LH ( DGLH ) abolished the stimulatory effect of LH on cAMP production by mature granulosa cells. DGLH , however, had no such inhibitory effect on the stimulatory activity of FSH, prostaglandin E2, isoproterenol, or choleragen. We have examined whether DGLH could prevent the desensitization of the cAMP response induced by continuous exposure to LH, or if it would induce receptor down-regulation. Cells were cultured with DGLH and LH concomitantly for a period of 3 h or 20 h and afterwards washed in acidic medium to dissociate bound ligands from their receptors. The cells were then challenged with fresh LH or with labeled 125I-human CG. At 20 h of culture with LH the cAMP response to the LH challenge was only 10% of the control, whereas after a 20-h culture with DGLH there was a 55% response to challenge with LH. DGLH , however, prevented LH from inducing desensitization in a dose-dependent manner (0.2-1.0 microgram/ml). Both LH and DGLH (1.0 microgram/ml each) markedly reduced (85%) the extent of binding of 125I-human CG to membrane receptors. At 3 h of culture, the cAMP response to challenge with LH was 25% of the control, whereas after 3-h culture with DGLH there was a 65% response to challenge with LH. DGLH (1.0 micrograms/ml) again prevented LH-induced desensitization, although only a moderate reduction in receptor-binding capacity (33%) by LH or DGLH was noted. The results suggest that occupancy of LH receptors alone for a long period is essential, but not sufficient to induce hormone desensitization. DGLH on its own is as active as LH in inducing a loss of membrane receptors, but causes only a moderate desensitization. The data support previous evidence that desensitization may result from postreceptor events, such as uncoupling of the receptors from the adenylate cyclase moiety, rather than receptor disappearance.

1-Methyl-3-isobutylxanthine↗
PubMedDate not supplied

Pituitary and testicular response to LH-RH and to a long-acting analogue (D-leu-6-LH-RH-ethylamide).

The LH, FSH and testosterone response to 50 microgram i.v. LH-RH and to 2.5, 5.0, 10.0, and 20.0 microgram i.m. D-Leu-6-LH-RH-ethylamide was studied in 6 subjects with normogonadotrophic, idiopathic oligozoospermia. All injections were given between 8:00 and 9:00 a.m. at weekly intervals. Blood samples were collected before and 30 and 45 minutes after injection of LH-RH, and before and 2, 4, 6, 12, and 24 hours after D-Leu-6-LH-RH-ethylamide injections. Serum levels of LH, FSH, and testosterone were measured by triplicate by R.I.A. LH and FSH responses to LH-RH showed peak values at 30 minutes, whereas following injections of D-Leu-6-LH-RH-ethylamide, maximal values were recorded between 4 and 6 hours and were higher than those obtained with LH-RH. A significant rise of serum testosterone levels was observed after all stimuli, with peak values 45 minutes after LH-RH and 4 to 6 hours after D-Leu-6-Lh-RH-ethylamide injections. The testosterone levels obtained following LH-RH and different doses of the analogue did not differ significantly from one another. The same sequence of maximal LH and FSH values was obtained after injections of LH-RH and of D-Leu-6-LH-RH-ethylamide, particularly at doses of 10.0 and 20.0 microgram. This suggests that the gonadotrophin response to these agents would be a true reflection of the individual mode of pituitary response.

Adult↗
PubMed1999

Evaluation of LH secretory dynamics during the rat proestrous LH surge.

The preovulatory luteinizing hormone (LH) surge results from the integration of complex interactions among gonadal steroids and hypothalamic and pituitary hormones. To evaluate changes in LH secretory dynamics that occur during the rat LH surge, we have 1) obtained frequently sampled serum LH concentration time series, 2) used both waveform-dependent and waveform-independent convolution analyses, and 3) independently assessed proestrous LH half-life and basal non-gonadotropin-releasing hormone (GnRH)-dependent LH secretion during the LH surge. Waveform-independent pulse analysis revealed a 24-fold increase in the maximal pulsatile LH secretory rate attained during late proestrus compared with early proestrus. A 15-fold increase was quantified for the mean LH secretory rate. In complementary analyses, we applied a measured LH half-life of 17 +/- 2.7 min and a median basal LH secretion rate of 0.0046 microgram. l-1. min-1 for convolution analysis, revealing a 16-fold increase in the mass of LH released/burst and more than sixfold rise in the amplitude of the secretory peaks. Evaluation of the approximate entropy of the LH surge profiles was performed, showing an increase in the orderliness of the LH release process during the surge. We conclude that both quantitative (mass/burst) and qualitative (approximate entropy) features of LH release are regulated during the proestrous LH surge.

Animals↗
PubMed1998

Luteinizing hormone (LH) stimulates both intracellular calcium ion ([Ca2+]i) mobilization and transmembrane cation influx in single ovarian (granulosa) cells: recruitment as a cellular mechanism of LH-[Ca2+]i dose response.

The gonadotropic hormones, LH and FSH, activate adenylyl cyclase in their respective target cells and thereby initiate many biochemical responses. In addition to stimulating cAMP production, both LH and FSH promote agonist-specific increases in the cytoplasmic concentration of free calcium ions ([Ca2+]i) in gonadal cells. Here, we have applied single cell fluorescence video microscopy with the Ca2+-sensitive dye fura-2 to investigate the mechanism(s) by which LH induces a rise in the [Ca2+]i in individual (swine) granulosa cells collected from single Graafian follicles. Stimulation with LH induced a rapid onset, biphasic, spike- and plateau-like [Ca2+]i signal in responsive granulosa cells. The cellular mechanisms mediating this biphasic LH-stimulated increase in [Ca2+]i were examined by external Ca2+ removal and via the manganese (Mn2+) quench technique, which showed that LH triggers initial intracellular Ca2+ mobilization followed by delayed transmembrane Ca2+ influx. Single cell Ca2+ assessment of the LH dose-response mechanism(s) revealed that higher concentrations of LH progressively recruit a larger number of responding individual granulosa cells. Further analyses disclosed a marked [Ca2+]i response heterogeneity among individual granulosa cells harvested from the same Graafian follicle. In addition, the percentage of cells responding to LH [but not to an alternative putative agonist of the phospholipase C (PLC) pathway, viz. endothelin-1] with a biphasic [Ca2+]i rise increased with maturational development of the follicle. Pretreatment of granulosa cells with a specific PLC inhibitor, U-73122 (but not with its inactive congener U-73343), significantly reduced the percentage of cells responding to a LH challenge from 78% to 25% (P < 0.0001) and prolonged the time required to achieve a half-maximal value of the [Ca2+]i transient, viz. from 22 +/- 1.5 sec (n = 27 cells) to 39 +/- 7.2 sec (n = 12 cells; P = 0.002). In cell population studies, LH stimulated in a concentration- and time-dependent manner the accumulation of inositol phosphate in porcine granulosa cells. In summary, the present single cell investigations in mature granulosa cells demonstrate that LH drives initial intracellular Ca2+ mobilization followed by transmembrane divalent cation influx. The PLC inhibitor U-73122 antagonizes this action of LH. By analyzing [Ca2+]i responses in individual living granulosa cells, we further show that, despite within-follicle diversity, the LH dose biphasic [Ca2+]i response arises via the recruitment of a larger number of responding gonadal cells rather than by increased [Ca2+]i signal amplitude. Finally, the percentage of individual LH (but not endothelin-1)-responding granulosa cells increases with follicular maturation. Collectively, these data highlight the potential importance of the LH-stimulatable, PLC-transduced [Ca2+]i signaling mechanism in the later stages of granulosa cell differentiation.

Animals↗
PubMed1976

Suppression of LH-RH-induced ovulation in hamsters and rats by synthetic analogues of LH-RH.

Peptide antagonists of LH-RH, [D-Phe2, D-Phe6]-LH-RH, [D-Phe2,D-Leu6]-LH-RH, [D-Phe2, D-Ala6]-LH-RH, [D-Phe2, D-Phe3,D-Phe6]-LH-RH, [DesHis2, D-Leu6]-LH-RH, and [DesHis2, D-Phe6]-LH-RH, were examined for their ability to suppress LH-RH-induced ovulation in phenobarbital-blocked hamsters and Nembutal-blocked rats. All of these peptides, with the exception of [DesHis2, Phe6]- LH-RH suppressed ovulation to various degrees, but alos exhibited various degrees of agonistic activities. Complete suppression of ovulation was achieved in rats with 3 mg [D-Phe2,Phe3,-D-Phe6]-LH-RH given in 4 divided doses at 30-min intervals starting 2 hr before the LH-RH injection. It was found that LH levels had to be lower than 5 ng/ml (control: 20-9 ng/ml) to suppress ovulation. However, the extent of suppression of ovulationdid not correlate with the serum LH levels less than 5 ng/ml. The incidence of ovulation induced by the intrinsic LH-RH activity of some of these analogues was similar to or greater than that resulting from administration of LH-RH plus analogue, suggesting that the activity of LH-RH itself was eliminated by pretreatment with the analogues.

Animals↗
PubMed1994

Diverse effects of a potent LH-RH antagonist on the LH and FSH release.

A potent LH-RH antagonist (Ac-D-Trp1,2, D-Cpa2, D-Lys6, D-Ala10 LH-RH (Antag) was used to study the differential regulation of FSH and LH secretion by endogenous LH-RH in ovariectomized (OVX) and regularly cycling rats. The endogenous LH-RH was suppressed by single injections of Antag in OVX animals and by long-term treatment with Antag in normal and OVX rats. Serum and pituitary LH and FSH, as well as serum estradiol (E2) and progesterone (P) was determined by RIA during and/or after the treatment. The direct effect of the antagonistic analog on the ovarian P release was tested in vitro using the isolated luteal cell system. Single injections of the Antag in OVX animals caused prompt and marked suppression of the serum LH (-80%), while no decrease of the serum FSH. Long-term treatment with the same analog decreased the serum LH by 50% but did not modify the serum FSH. In normal rats, serum LH dropped to undetectable levels, while serum FSH did not change significantly. Long-term treatment with the antagonist also resulted in divergent alterations in the pituitary gonadotropin concentrations. In OVX animals, the pituitary LH content moderately elevated (+21%), however, the FSH did not change. In normal rats, ovarian cycles were interrupted, and no ovulation appeared during the treatment. The pituitary LH concentration increased by 46%, while the FSH decreased by 43%. Marked depression was found in the serum P (-60%) but no significant change in the serum E2 levels. Incubation of isolated luteal cells with the Antag did not influence the HCG-induced P secretion in vitro, demonstrating that the in vivo inhibitory effect of the antagonistic LH-RH analog on the P secretion asserts not directly on the ovarian LH-RH receptors, but through inhibition of the endogenous LH-RH. Our studies give evidence that the long-term treatment with LH-RH antagonist suppress the LH and P but not the FSH and E2 secretion, and provide new data suggesting the presence of a FSH-releasing factor in the CNS.

Amino Acid Sequence↗
PubMed1998

Recombinant human luteinizing hormone (LH) to support recombinant human follicle-stimulating hormone (FSH)-induced follicular development in LH- and FSH-deficient anovulatory women: a dose-finding study. The European Recombinant Human LH Study Group.

The efficacy of recombinant human LH (rhLH) for supporting human (rhFSH)-induced follicular development was investigated in hypogonadotropic hypogonadal women (WHO group I anovulation). Patients (n = 38) were randomized to receive rhLH (0, 25, 75, or 225 IU/day) in addition to a fixed dose of rhFSH (150 IU/day). rhLH was found 1) to promote dose-related increases in estradiol (E2) and androstenedione secretion by rhFSH-induced follicles, i.e. serum concentrations on the last day of FSH administration were 65 +/- 4, 195 +/- 94, 1392 +/- 585, and 2441 +/- 904 pmol/L for E2 and 3.6 +/- 0.9, 5.1 +/- 1.3, 6.4 +/- 1.3, and 6.7 +/- 1.3 nmol/L for androstenedione for patients treated with 0, 25, 75, and 225 IU rhLH, respectively; 2) to increase ovarian sensitivity to FSH, as demonstrated by the proportion of patients who developed follicles after the administration of a fixed dose of FSH, i.e. 1 of 8, 3 of 7, 7 of 9, and 8 of 10 in patients treated with 0, 25, 75, and 225 IU rhLH, respectively; and 3) to enhance the ability of these follicles to luteinize when exposed to hCG. A daily dose of 75 IU rhLH was effective in the majority of women in promoting optimal follicular development (defined as > or = 1 follicle > or = 17 mm; E2, > or = 400 pmol/L; midluteal phase progesterone, > or = 25 nmol/L) and maximal endometrial growth. A minority of patients may require up to 225 IU/day. rhLH, given sc at a dose up to 225 IU/day, was not immunogenic and was well tolerated.

Adult↗
PubMed1987

Short-term pituitary desensitization to luteinizing hormone-releasing hormone (LH-RH) after pulsatile LH-RH administration in women with amenorrhea of suprapituitary origin.

The existence of a short-term pituitary desensitization in luteinizing hormone (LH) release to single doses of luteinizing hormone-releasing hormone (LH-RH) in the ovariectomized rat was recently disclosed. The purpose of the present study was to investigate whether this refractoriness is also present in humans. Blood from six women with amenorrhea of suprapituitary origin was sampled every 10 minutes for 300 minutes for determination of LH and follicle-stimulating hormone (FSH). A pulse of 20 micrograms LH-RH was given intravenously 90 and 210 minutes after the first blood sample, and 2 micrograms LH-RH was given 30, 150, 240, and 270 minutes after t0. The mean maximal increments of LH and FSH were compared. The LH response to a 2-micrograms LH-RH bolus given 30 (t240) or 60 (t150) minutes after a 20-micrograms LH-RH pulse was significantly decreased, compared with the initial response to this dose at t30. For both LH and FSH, the response to 2 micrograms LH-RH given 30 minutes after the 20-micrograms pulse (t240) was almost absent, compared with 60 (t150) minutes after the 20-micrograms dose. We conclude that a short-term pituitary refractoriness to LH-RH is present after administration of single pulses of LH-RH in women with amenorrhea of suprapituitary origin and pulses of LH-RH in the physiologic range (2 micrograms) given to these women do not always generate LH and FSH increments that are identifiable as significant hormone pulses.

Adult↗
PubMed2002

Targeted cytotoxic analogue of luteinizing hormone-releasing hormone (LH-RH) only transiently decreases the gene expression of pituitary receptors for LH-RH.

A cytotoxic analogue of LH-RH, AN-207, consisting of 2-pyrrolinodoxorubicin (AN-201) linked to carrier [D-Lys6]LH-RH, was developed for targeted therapy of cancers expressing LH-RH-receptors. To determine its possible side-effects on the pituitary gland, we investigated the gene expression of pituitary LH-RH-receptors and LH secretion in ovariectomized female and normal male rats after treatment with the maximum tolerated dose of AN-207. The effect of AN-207 on the gene expression of the pituitary GH-RH-receptors and GH secretion was also assessed in male rats. Five hours after a single i.v. injection of AN-207 at 175 nmol/kg, there was a 39-51% decrease in mRNA expression for the pituitary LH-RH-receptors in male and female rats. The carrier, at an equimolar dose, caused a similar reduction (37-39%), whereas the cytotoxic radical AN-201, at an equitoxic dose (110 nmol/kg), produced only a 12-24% decrease (NS) in the mRNA expression of LH-RH-receptors. AN-207 and the carrier analogue induced a comparable 90-100-fold increase in serum LH concentrations in male rats, and the same 12-fold elevation in OVX rats at 5 h. Seven days after treatment with AN-207, the mRNA levels for the LH-RH receptors and the serum LH concentration were back to normal in both sexes. AN-207, the carrier, and AN-201 had no significant effect on the expression of mRNA for GH-RH-receptors in the pituitary. In vitro, a continuous perfusion of pituitary cells with 10 nM AN-207 did not affect the hormone-releasing function of the targeted LH cells or the nontargeted GH cells. Our results demonstrate that cytotoxic LH-RH analogue AN-207, at the maximum tolerated dose causes only a transient decrease in the gene expression of the pituitary LH-RH receptors, and the levels of mRNA for LH-RH receptor fully recover within 7 days. Moreover, the carrier hormone moiety, and not the cytotoxic radical in AN-207 is responsible for this transient suppression. Our findings suggest that the therapy with cytotoxic LH-RH analogues will not inflict permanent damage to pituitary function.

Animals↗
PubMed1996

Down-regulation of pituitary receptors for luteinizing hormone-releasing hormone (LH-RH) in rats by LH-RH antagonist Cetrorelix.

Antagonists of luteinizing hormone-releasing hormone (LH-RH), unlike the LH-RH agonists, suppress gonadotropins and sex steroid secretion immediately after administration, without initial stimulatory effects. [Ac-D-Nal(2)1,D-Ph(4Cl)2,D-Pal(3)3,D-Cit6,D-Ala10]LH-R H (SB-75; Cetrorelix) is a modern, potent antagonistic analog of LH-RH. In this study, the binding characteristics of receptors for LH-RH in membrane fractions from rat anterior pituitaries were investigated after a single injection of Cetrorelix at a dose of 100 microg per rat. To determine whether the treatment with Cetrorelix can affect the concentration of measurable LH-RH binding sites, we applied an in vitro method to desaturate LH-RH receptors by chaotropic agents such as manganous chloride (MnCl2) and ammonium thiocyanate (NH4SCN). Our results show that the percentages of occupied LH-RH receptors at 1, 3, and 6 h after administration of Cetrorelix were approximately 28%, 14%, and 10%, respectively, of total receptors. At later time intervals, we could not detect occupied LH-RH binding sites. Ligand competition assays, following in vitro desaturation, demonstrated that rat pituitary LH-RH receptors were significantly (P < 0.01) down-regulated for at least 72 h after administration of Cetrorelix. The lowest receptor concentration was found 3-6 h after Cetrorelix treatment and a recovery in receptor number began within approximately 24 h. The down-regulation of LH-RH binding sites induced by Cetrorelix was accompanied by serum LH and testosterone suppression. Higher LH-RH receptor concentrations coincided with elevated serum hormone levels at later time intervals. Our results indicate that administration of LH-RH antagonist Cetrorelix produces a marked down-regulation of pituitary receptors for LH-RH and not merely an occupancy of binding sites.

Animals↗
PubMed1979

Inhibitory control of the pituitary LH secretion by LH-RH in male rats.

Luteinizing hormone-releasing hormone (LH-RH) was administered to prepubertal male rats (intact, castrate or castrate-adrenalectomized, 60 g body weight) for 28 days (1 microgram LH-RH/day, s.c.), at a 10-fold physiological dose, as compared to the minimal FSH-releasing dose of 100 ng/rat s.c. In intact rats, serum LH and weight of androgen-dependent organs (vented prostate, seminal vesicles) were reduced after 14 days of treatment. In castrate rats, the postcastration rise in serum LH was abolished by treatment. Pituitary LH content, FSH secretion and prolactin secretion were not suppressed. Hypothalamic LH-RH was increased at 14 and 21 days. In castrate adrenalectomized male rats, LH secretion was also suppressed by 1 microgram LH-RH s.c. x 28 days. The hypothalamic LH-RH content did not increase. The pituitary LH-RH receptor level was not down-regulated after 14 days treatment either in intact or castrate male rats. Pituitary inhibition (LH release) in rats by a supraphysiological dose of LH-RH given for 28 days indicates that the optimal regime for chronic treatment has to be determined by monitoring LH release at regular intervals. Direct pituitary inhibition by LH-RH may explain some of the unexpected antifertility effects observed with high doses of LH-RH.

Adrenal Glands↗
PubMed1977

Application of ovine luteinizing hormone (LH) radioimmunoassay in the quantitation of LH in different mammalian species.

A sensitive double antibody radioimmunoassay has been developed for measuring luteinizing hormone (LH) in various African mammalian species, using rabbit anti-ovine LH serum (GDN 15) and radioiodinated rat LH or ovine LH. Serum and pituitary homogenates from some African mammals (hyrax, reedbuck, sable, impala, tsessebe, thar, spring-hare, ground squirrel and cheetah, as well as the domestic sheep, cow and horse and laboratory rat and hamster) produced displacement curves parallel to that of the ovine LH standards. The specificity of the assay was examined in detail for one species, the rock hyrax. Radioimmunoassay and bioassay estimates of LH in hyrax pituitaries containing widely differing quantities of pituitary hormones were similar. In sexually active male hyrax mean plasma LH was 12.1 ng/ml and pituitary LH 194 microgram/gland, but in sexually quiescent hyrax mean plasma LH was 2.4 ng/ml and mean pituitary LH 76 microgram/gland. Intravenous injection of 10 microgram of luteinizing hormone releasing hormone increased mean LH levels in hyrax from 0.9 ng/ml to 23.2 ng/ml by 30 min. Conversely, im injection of 250 microgram testosterone induced a fall in LH levels in male hyrax from 1.7 ng/ml to 0.7 ng/ml 6 h after administration. Although the specificity of the assay for quantitating plasma LH in other species was not categorically established, there was a good correlation between plasma LH concentration and reproductive state in the bontebok, impala, spring-hare, thar, cheetah, domestic horse and laboratory rat, suggesting the potential use of the antiserum in quantitating LH in a variety of mammalian species.

Animals↗
PubMed1992

Heightened secretion by small and medium-sized luteinizing hormone (LH) gonadotropes late in the cycle suggests contributions to the LH surge or possible paracrine interactions.

LH secretion from pituitary cell fractions separated by centrifugal elutriation was compared to learn whether any contributed to the LH surge. After plating (1 h) and stimulation with 0-10 nM [D-Lys6]GnRH (4 h), some fractions secreted levels that were out of proportion to their enrichment. Large cells from proestrous morning rats (3-fold enriched) secreted 4.3 times more LH, and medium-sized fractions (1.5-fold enriched) secreted 2-3.4 times more LH than unseparated cells during estrus or metestrus. Normalized data (nanograms per 20,000 cells) showed that basal levels reflected the enrichment in the fractions. Data were also normalized to nanograms of LH per 1,000 LH gonadotropes to focus on LH cell activity. Basal secretion in unseparated cultures (4-6 ng/ml/1,000 LH cells) was lower than that in small or large LH cells during all stages except proestrus, when small gonadotropes became as active as those in unseparated cultures, and large gonadotropes secreted 2-3 times more LH. Basal secretion from medium-sized gonadotropes was comparable to that in unseparated cultures. [D-Lys6]GnRH-mediated secretion from unseparated, small, and large LH cells was comparable during most stages. However, during proestrus, large gonadotropes secreted 2.2 times more LH than unseparated counterparts. Stimulated medium-sized LH cells were 1.3-2.3 times more active in most stages than those in unseparated cultures and 1.75-2.8 times more active than those in large cell fractions (from proestrous PM to metestrus). Whereas this enhanced secretion late in proestrus suggests that medium-sized LH cells may support the LH surge, it also may reflect the removal of regulatory factors from cells in other fractions. Studies of autocrine or paracrine interactions with gonadotropes are needed to test this hypothesis.

Animals↗
PubMed1984

The luteinizing hormone-releasing hormone (LHRH) agonist [D-Trp6-Pro9-NEt]LHRH increased rather than lowered LH and alpha-subunit levels in a patient with an LH-secreting pituitary tumor.

Episodic secretion of LH, and the responses of serum LH, alpha-subunit, and testosterone concentrations to the acute administration of LHRH and the chronic administration of the LHRH agonist analog [D-Trp6-Pro9-NEt]LHRH (D-Trp6-Pro9) were evaluated in a 33-yr-old man previously reported to have an LH-secreting pituitary tumor unaccompanied by FSH hypersecretion. Basal serum LH and alpha-subunit concentrations were elevated [57 +/- 0.7 (SEM) mIU/ml (range, 45-71) and 26 ng/ml, respectively]. Frequent sampling revealed six LH secretory spikes over a 24-h period with increments above basal levels varying from 23-40% and interspike intervals ranging from 1.5-5 h. The concentrations of LH or alpha-subunit after iv administration of 150 micrograms LHRH did not increase above these intrinsic LH secretory increments (delta LH: 23%; delta alpha-subunit: 21%). The low basal serum FSH concentrations (3.5 mIU/ml) and elevated basal serum testosterone levels (1480 ng/dl) were unchanged after LHRH. Administration of clomiphene citrate produced no increase in serum LH, FSH, or testosterone concentrations. An attempt was made to decrease LH secretion in this patient using D-Trp6-Pro9. Administration of 200 micrograms daily sc of this LHRH analog for 21 days was associated with increases in serum LH and alpha-subunit concentrations. Mean serum LH and alpha-subunit levels for the 21 days of analog administration were 110 +/- 5.4 (SEM) mIU/ml (range, 70-170) and 64 +/- 3 (SEM) ng/ml (range, 32-84), respectively. During the 9-day period after discontinuance of the LHRH analog, levels of both serum LH and alpha-subunit declined precipitously and mean serum LH and alpha-subunit levels were 58 +/- 7 (SEM) mIU/ml (range, 18-90) and 22 +/- 3 (SEM) ng/ml (range, 12-44), respectively. We conclude that this patient's pituitary tumor has diminished responsiveness to acute LHRH administration and that the effect of chronic D-Trp6-Pro9 is stimulatory rather than inhibitory, as occurs after chronic administration of this analog to normal subjects. The blunted responsiveness to LHRH administration and the lack of response to clomiphene citrate suggest tumor autonomy. The presence of modest paradoxical responsiveness of serum LH and alpha-subunit concentrations during the course of daily D-Trp6-Pro9 administration suggests that central regulatory mechanisms, if present, are abnormal.

Adenoma↗
PubMed2000

Replenishment of LH stores of gonadotrophs in relation to gene expression, synthesis and secretion of LH after the preovulatory phase of the sheep oestrous cycle.

The pattern of replenishment of LH secretory granule stores in sheep pituitary gonadotrophs, after an induced LH surge, was determined by immunogold localisation at the ultrastructural level by electron microscopy. Twenty-four Welsh Mountain ewes were initially synchronised with progestagen devices for 14 days before luteolysis was induced by a prostaglandin F(2 alpha) analogue, cloprostenol. A further 24 h later, a preovulatory LH surge was induced by intravenous injection of a GnRH agonist, buserelin. Animals were divided into four groups (n=6) and blood sampled at 2 h intervals from 4 h prior, to 18 h after, buserelin administration and then at infrequent intervals (1 to 8 h) thereafter until death. Pulse profiles of LH were also obtained by an additional collection of blood samples within a 6 h window directly preceding death. Groups of animals were killed at 24, 48, 72 or 96 h after buserelin treatment. Pituitaries were dissected and processed for transmission electron microscopy and frozen for later molecular biological analysis. A characteristic preovulatory surge of LH was observed in all animals. The cytoplasm of gonadotrophs, in animals killed 24 h after buserelin treatment, was completely empty of secretory granules. This was associated with diminutive pituitary LH content, low pituitary GnRH binding levels and an almost complete absence (one pulse in one animal) of LH pulsatile secretion. Despite the lack of apparent secretory activity, clusters of exposed LH beta label present within the cytoplasm at this time and constant LHbeta mRNA expression levels irrespective of tissue collection time, suggest that the cell is actively synthesising LHbeta. The formation of sparse numbers of small LH beta immuno-labelled electron-dense secretory granules was apparent at 48 h after buserelin treatment, and replenishment of LH beta immuno-labelled granule stores continued until total granule numbers had increased two-fold (P<0.01) by 96 h post-treatment. Affiliated with granule replenishment was a significant increase in pituitary LH content (P<0.01), pituitary GnRH binding levels (P<0.01) and the restoration of LH pulsatile secretion. Despite the replenishment of granule stores with time, cytoplasmic area did not vary. These results suggest that restoration of pulsatile LH secretion after a preovulatory LH surge is related to replenishment of LH beta secretory granule stores and an increase in GnRH binding levels.

Analysis of Variance↗
PubMed1975

Plasma gonadotropin (LH and FSH) concentrations in repubertal and pubertal children upon stimulation by LH-releasing hormone.

The simultaneous determination of LH and FSH were carried out in a single plasma sample by double antibody radioimmunoassays in a total of 26 prepubertal and pubertal children. The blood samples were taken before and after i.v. application of 25 mug synthetic LH-RH. Plasma LH and FSH concentrations found in prepubertal boys and girls at beginning of the test and at the time of maximum response were compared with those measured in pubertal boys and girls. The mean basal levels of LH and FSH are in group I (8 prepubertal girls): LH 0.6+/-0.7 (SD) mIU/ml, FSH 1.5+/-0.8 mIU/ml; in group II (6 prepubertal boys): LH 1.8+/-1.0 mIU/ml, FSH 2.0+/-0.8 mIU/ml; in group III (6 pubertal girls): LH 4.1+/-2.0 mIU/ml, FSH 4.7+/-2.8 mIU/ml; in group IV (6 pubertal boys): LH 3.5+/-2.3 mIU/ml, FSH2.0+/-1.2 mIU/ml. The mean maximum response of LH and FSH after stimulation are in group I: LH 4.1+/-2.3 mIU/ml, FSH 11.7+/-3.7 mIU/ml; in group II: LH 4.2+/-1.0 mIU/ml, FSH 6.0+/-1.1 mIU/ml; in group III: LH 19.7+/-10.6 mIU/ml, FSH 12.8+/-5.7 mIU/ml; in group IV: LH 13.4+/-5.7 mIU/ml, FSH 3.8+/-0.9 mIU/ml. It is suggested that without stimulation of the pituitary with LH-RH, plasma LH and FSH levels are not reliable parameters to test the pituitary gonadotropin reserve.

Adolescent↗
PubMed1997

Differential expression of the two closely related LIM-class homeobox genes LH-2A and LH-2B during limb development.

We have isolated the chicken homeobox genes LH-2A and LH-2B encoding two related LIM domain-containing homeodomain proteins and examined the expression pattern during chick limb development. LH-2A is most closely related to human and rat LH-2, while LH-2B is less conserved. Although both LH-2A and LH-2B are expressed in the limb mesenchyme throughout stage 16 to stage 32, LH-2A transcripts are detectable in the distal limb bud and LH-2B transcripts are detectable in the anterior limb bud. Signals from the apical ectodermal ridge positively regulate LH-2A expression, since removal of the apical ectoderm resulted in the rapid reduction of LH-2A expression in the distal limb mesenchyme. Ectopic expression of the sonic hedgehog gene in the anterior margin of the limb bud resulted in the rapid reduction of LH-2B expression accompanying respecification of the positional value to the posterior phenotype. These results suggest that LH-2A and LH-2B play important roles in the determination and specification of the proximal-distal and anterior-posterior positional values, respectively.

Amino Acid Sequence↗