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PubMed1975

Human pituitary luteinizing hormone. Isolation and characterization of four glycoproteins with luteinizing activity.

Two major and two minor components of human luteinizing hormone (lutropin) were isolated from whole frozen pituitaries by a procedure involving extraction of homogenized pituitaries, (NH4)2SO4 fractionation, chromatography on DEAE-cellulose, Sephadex G-100, and SE-Sephadex C-50 and electrophoresis in polyacrylamide gel. The isolation procedure was monitored by both bioassays and radioimmunoassays. Contamination of the final products by other pituitary hormone activities was very low. The four lutropin components were all homogeneous by polyacrylamide gel electrophoresis (a sieving medium) and by free zone electrophoresis (a non-sieving medium). No heterogeneity was observed when the components were studied in the ultracentrifuge by sedimentation-equilibrium technique. The molecular weights of the components were in the range of 34 000-40 000. Sedimentation velocity experiments with the two major components revealed in each case one boundary with S20,W values of 3.2 S and 3.5 S. Further evidence for the homogeneity of the components was the observation of only one precipitin line for each component upon immunodiffusion against a rabbit anti-human lutropin serum. Amino acid and carbohydrate analyses indicated close similarity among the four components. From the analysis data the molecular weights of the components were calculated to be 31 000-33 000.

Amino Acids↗

PubMed1977

Radioreceptorassay of luteinizing hormone-human chorionic gonadotropin in urine: detection of the luteinizing hormone surge and pregnancy.

A radioreceptorassay of luteinizing hormone (LH)-human chorionic gonadotropin (hCG), using plasma membranes of bovine corpora lutea, has been extended to the detection of the midcycle LH peak and subsequent pregnancy in morning and 24-hour urine samples on days 10 to 12 following ovulatiobjects as determined by radioreceptorassay and radioimmunoassay were 45 ng and 20 ng/ml of urine, respectively; in 24-hour urine samples, mean levels of 39 ng and 17 ng of LH/ml, respectively, were found. A sustained rise in hCG was detected by the radioreceptorassay from 10 to 12 days after conception, and by day 15 the hCG levels were in the range of the midcycle LH range; this finding was confirmed by the radioimmunoassay of hCG.

Adult↗

PubMed1981

A new hypothalamic substance, and not luteinizing hormone-releasing hormone, is detected immunocytochemically by antibody to luteinizing hormone-releasing hormone.

Adjacent paraffin sections of rat hypothalami fixed in Bouin's fluid were treated either with buffer or with luteinizing hormone-releasing hormone (LHRH) before immunocytochemical staining with anti-LHRH. Upon buffer pretreatment, pituitary gonadotrophs were unstained and hypothalamic fibers were stained. Upon LHRH pretreatment, pituitary gonadotrophs were stained (receptor reaction) and hypothalamic fibers were unstained. Extension of washes and use of series of neutralizing antisera between LHRH application and immunocytochemical staining, as well as the absence of inhibiting concentrations of LHRH in the later washes and neutralizing antisera removed from the sections, excluded the possibility that the disappearance of visualization of hypothalamic fibers was due to blockage of anti-LHRH in immunocytochemical staining. The results suggested that LHRH removed from the sections an immunocytochemically stainable but as yet unknown analog of LHRH and replaced it with LHRH, which in turn became lost during subsequent immunocytochemical processing. This idea was confirmed by the isolation by high-pressure liquid chromatography of a peak, distinct from LHRH, upon treatment of hypothalami with LHRH. It is suggested that the new substance may be carrier-held and that this substance, rather than LHRH, is normally detected by immunocytochemistry with anti-LHRH. Added LHRH binds not only to high-affinity pituitary receptors but also to low-affinity hypothalamic carriers.

Animals↗

PubMed1988

Receptors for prolactin, somatostatin, and luteinizing hormone-releasing hormone in experimental prostate cancer after treatment with analogs of luteinizing hormone-releasing hormone and somatostatin.

Membrane receptors for luteinizing hormone-releasing hormone (LH-RH), somatostatin, and prolactin (PRL) were investigated in the Dunning R-3327H rat prostate adenocarcinoma specimens after in vivo treatment with microcapsules of the agonist [D-Trp6]LH-RH and the somatostatin analog RC-160. The LH-RH receptors showed a low-binding affinity (Kd = 54 nM) and high capacity (Bmax = 12.0 pmol/mg). Treatment with the [D-Trp6]LH-RH decreased the binding affinity (Kd = 0.52 microM). Specific somatostatin receptors, with Kd = 1.3 nM and Bmax = 543 fmol/mg, were also found. Treatment with [D-Trp6]LH-RH lowered Bmax to 44 fmol/mg, and administration of RC-160 reduced Kd to 30 nM. After the combined treatment with the two analogs, Kd and Bmax were decreased. Specific PRL receptors (Kd = 0.72 nM; Bmax = 161 fmol/mg) were also detected. Treatment with either analog reduced Bmax by 50%, but a much greater reduction of PRL binding capacity was revealed after in vitro dissociation of the bound endogenous PRL by MgCl2. The dramatic fall in the total number of PRL receptors after combination treatment with both analogs could be partially responsible for the decrease in the weight and volume of prostate tumors. The findings support the concept that analogs of LH-RH and somatostatin can inhibit tumors directly through their own respective receptors. One of several mechanisms of the antineoplastic activity of these analogs could be the elimination of tumor growth-promoting effect of PRL by the reduction of the total number of PRL receptors.

Adenocarcinoma↗

PubMed2005

Regulation of luteinizing hormone receptor expression: evidence of translational suppression in vitro by a hormonally regulated mRNA-binding protein and its endogenous association with luteinizing hormone receptor mRNA in the ovary.

Our previous studies have identified a luteinizing hormone receptor (LHR) mRNA-binding protein (LRBP) that binds to the coding region (LBS) of rat LHR mRNA. The identity of LRBP was later established as mevalonate kinase (MVK). The present study examined if LRBP binding to LHR mRNA impairs translation. A full-length FLAG-tagged rat LHR mRNA was synthesized and translated in vitro. The translation product was immunoprecipitated and analyzed on SDS-PAGE. The addition of LRBP inhibited LHR mRNA translation. This inhibitory effect was reversed by an excess of wild type (wt) LBS. To determine whether this reversal of the inhibitory effect of LRBP was indeed due to the sequestration of LRBP by the wtLBS, a translation reaction was performed in the presence of mutated LBS in which all the cytidine in the wtLBS was mutated to uridine. This mutation of LBS has been shown to render it incapable of interacting with LRBP. Unlike wtLBS, the mutated LBS was unable to reverse the inhibitory effect of LRBP on LHR mRNA translation. The addition of mevalonate, which has been shown to compete for LHR mRNA binding to LRBP, also reduced the extent of translation inhibition by LRBP. Endogenous association of LHR mRNA with MVK was assessed by immunoprecipitation of the ribonucleoprotein complex with MVK antibody followed by reverse transcription-PCR of the RNA associated with the immune complex. Amplification of LHR mRNA, if any, associated with the immunoprecipitate obtained from ovarian ribonucleoprotein complex with gene-specific primers confirmed the association of LHR mRNA with MVK. Collectively, the present data support the novel function of LRBP as a translational inhibitor of LHR mRNA in the ovary.

Animals↗

PubMed2004

Chemohormonal therapy as primary treatment for metastatic prostate cancer: a randomized study of estramustine phosphate plus luteinizing hormone-releasing hormone agonist versus flutamide plus luteinizing hormone-releasing hormone agonist.

BACKGROUND: The present study was undertaken mainly to investigate whether chemohormonal therapy with estramustine phosphate plus luteinizing hormone-releasing hormone (LHRH) agonist has a more beneficial effect than the hormonal therapy with flutamide plus LHRH agonist for newly diagnosed patients with metastatic prostate cancer. METHODS: A total of 57 patients with metastatic prostate cancer aged 59-80 years (median 74 years) were entered in the study and were randomized to the treatment of estramustine phosphate (560 mg/day) plus LHRH agonist (estramustine group) or flutamide (375 mg/day) plus LHRH agonist (flutamide group) with stratification for the degree of performance status, histological differentiation and bone metastasis. RESULTS: Both of the treatment regimens were well tolerated with similar incidences of adverse drug reactions. The overall response rates (complete response plus partial response) at 12 weeks after treatment in the estramustine and flutamide groups were 76 and 55%, respectively. The median time to objective progression for the estramustine group (25.4 months) was longer than that of the flutamide group (14.6 months). The serum levels of follicle stimulating hormone and testosterone were significantly lower in the estramustine group. CONCLUSIONS: Chemohormonal therapy with estramustine phosphate plus LHRH agonist showed longer clinical progression-free survival than the hormonal therapy with flutamide plus LHRH agonist (P = 0.03), although there was no significant difference in the overall survival. A larger-scaled trial with more statistical power is required to clarify that the former regimen is more beneficial than the latter for newly diagnosed patients with advanced prostate cancer.

Aged↗

PubMed2005

Human malignant melanomas express receptors for luteinizing hormone releasing hormone allowing targeted therapy with cytotoxic luteinizing hormone releasing hormone analogue.

Cytotoxic analogue of luteinizing hormone releasing hormone (LHRH), AN-207, binds with high affinity to LHRH receptors and can be targeted to tumors expressing these receptors. We investigated the expression of LHRH receptors in surgical specimens of human malignant melanoma and evaluated the effects of AN-207 in models of human melanoma. Human melanoma specimens derived from primary tumors or metastases were examined for LHRH receptor expression by immunohistochemistry. Binding assays, Western immunoblotting, and reverse transcription-PCR analyses were used to investigate LHRH receptors in MRI-H255 and MRI-H187 transplantable human melanoma tumor lines. Antitumor effects of AN-207 and its components were evaluated in vivo in nude mice bearing xenografts of either melanoma tumor line. All 19 human melanoma specimens examined showed positive staining for LHRH receptors. The mRNA for LHRH receptors, receptor protein and binding sites for LHRH were detected in both transplantable melanoma tumor lines. AN-207 significantly inhibited the growth of MRI-H255 and MRI-H187 xenografts in vivo, reducing tumor volume by 59.9% to 79.2% and tumor weight by 61.0% to 76.9% (all P < 0.05). The components of AN-207 (LH-RH analogue carrier and cytotoxic radical AN-201 as single drugs or as an unconjugated mixture) had no significant effects. Blockade of LHRH receptors by an excess of LHRH agonist Decapeptyl suppressed the effects of AN-207. LHRH receptors are expressed in a very high percentage of human malignant melanoma specimens and can be used for targeted chemotherapy with cytotoxic LHRH analogue AN-207.

Animals↗

PubMed2005

Receptors for luteinizing hormone releasing hormone expressed on human renal cell carcinomas can be used for targeted chemotherapy with cytotoxic luteinizing hormone releasing hormone analogues.

PURPOSE: To determine the expression of luteinizing hormone releasing hormone (LHRH) receptors in specimens and cell lines of human renal cell carcinoma (RCC) and to evaluate the antitumor efficacy of targeted therapy with a cytotoxic analogue of LHRH, AN-207, in vivo. AN-207, consisting of [D-Lys(6)] LHRH linked to a cytotoxic radical, 2-pyrrolinodoxorubicin (AN-201), binds with high affinity to LHRH receptors and can be targeted to tumors expressing these receptors. EXPERIMENTAL DESIGN: The expression of LHRH receptors was investigated in 28 surgically removed specimens of human renal cell carcinoma (RCC) by immunohistochemistry and in three human RCC cell lines A-498, ACHN, and 786-0 by radioreceptor assays, Western immunoblotting, and reverse transcription-PCR analysis. Antitumor efficacy of AN-207 was examined in experimental models of these cell lines. RESULTS: Positive staining for LHRH receptors was found in all (28 of 28) of the examined human RCC specimens. mRNA for LHRH receptor, receptor protein, and LHRH binding sites were detected in all three cell lines. AN-207 significantly (P < 0.05) inhibited the growth of A-498, ACHN, and 786-0 xenografts in vivo producing a 67.8% to 73.8% decrease in tumor volume and a 62.2% to 77.3% reduction in tumor weight. Nontargeted cytotoxic radical AN-201 had no significant antitumor effects. Blockade of LHRH receptors by an excess of LHRH agonist Decapeptyl suppressed tumor inhibitory effects of AN-207. CONCLUSIONS: Our findings indicate that LHRH receptors are expressed in human RCC specimens and can be used for targeted chemotherapy with cytotoxic LHRH analogues.

Animals↗

PubMed1992

Evidence for dual coupling of the murine luteinizing hormone receptor to adenylyl cyclase and phosphoinositide breakdown and Ca2+ mobilization. Studies with the cloned murine luteinizing hormone receptor expressed in L cells.

The murine receptor for luteinizing hormone (LHR) was cloned and expressed in L cells. This LHR (mature protein of 674 amino acids) is very similar to that of the rat (same length, 36 amino acid differences) but differs significantly more from that of man (673 amino acids, 109 differences). Expression of the murine LHR in L cells led to the appearance of binding sites for human chorionic gonadotropin (hCG) with a Kd of 150 pM and an LH- and hCG-stimulable adenylyl cyclase activity (EC50 = 50-100 pM hCG). Upon labeling pools of phosphoinositides with [3H]myo-inositol, L cells expressing the murine LHR responded to hCG with an increase in their rate of phosphoinositide hydrolysis (EC50 = 2,400 pM hCG). This was accompanied by an increase in intracellular Ca2+ [( Ca2+]i), as determined by the Fura2 method. This increase in [Ca2+]i in response to hCG was dependent on the LHR, for HCG did not affect [Ca2+]i in L cells not expressing the LHR. The effect was not due to the cAMP-forming activity of the LH receptor, for neither forskolin nor prostaglandin E1, which both increase cAMP levels in L cells, had a similar effect in either control or LHR-expressing cells and isoproterenol had no effect in L cells expressing a functionally active hamster beta-adrenergic receptor. The effect was also not due to overexpression of a Gs-coupled receptor, for L cells expressing 8-fold higher levels of the human V2 vasopressin receptor did not mimic the Ca(2+)-mobilizing response of the LH receptor. We conclude that the LH receptor has the capability of activating two intracellular signaling pathways: one leading to stimulation of adenylyl cyclase and resulting in increases in cAMP and a second leading to stimulation of phospholipase C and resulting in formation of inositol phosphates and elevations in [Ca2+]i. These data correlate positively with and provide a mechanistic explanation for previous reports on the ability of hCG to mobilize phosphoinositides and increasing [Ca2+]i in luteal and granulosa cells (e.g. Davis, J. S., West, L. A., and Farese, R. V. (1984) J. Biol. Chem. 259, 15028-15034).

Adenylyl Cyclases↗

PubMed1972