Luteinizing Hormone-Releasing Hormone (LHRH) and LHRH Agonist Termination of Pregnancy in Hypophysectomized Rats: Extrapituitary Site of Action*

Bex, Frederick J.; Corbin, Alan

doi:10.1210/endo-108-1-273

Cited by 48 publications

(18 citation statements)

References 32 publications

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“…Highly purified human pituitary FSH (human FSH-I1, NIDDK) was iodinated by the lactoperoxidase-glucose oxidase method [14]. Following separation of protein-bound and free 125 I by Sephadex G-100 column chromatography, 125 I-labelled FSH was further purified by concanavalin A chromatography as described by Dufau et al [15]; the specific activity of 125 I-labelled FSH was 75–85 µCi/µg protein.…”

Section: Methodsmentioning

confidence: 99%

A Naturally Occurring Basically Charged Human Follicle-Stimulating Hormone (FSH) Variant Inhibits FSH-Induced Androgen Aromatization and Tissue-Type Plasminogen Activator Enzyme Activity in vitro

et al. 1998

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It is well known that deglycosylation of gonadotropins by enzymatic or chemical procedures or by deletion of sites for N-linked glycosylation produces antagonistic analogs which are able to interact strongly with the receptor and to inhibit binding of the wild-type hormone. In the present study, we analyzed the antagonistic properties of a naturally occurring basic follicle-stimulating hormone (FSH) charge isoform obtained after high-resolution chromatofocusing of human anterior pituitary glycoprotein extracts. Coincubation of increasing amounts of this isoform with a highly purified human pituitary FSH preparation or with recombinant human FSH at doses equivalent to their corresponding ED₅₀ for estradiol and tissue-type plasminogen activator (tPA) production, inhibited FSH-induced estrogen production and tPA enzyme activity by cultured rat granulosa cells in a dose-dependent manner. These inhibitory effects were apparently exerted at steps following 3′,5′-cyclic adenosine monophosphate (cAMP) formation and did not involve activation of the protein kinase C pathway since: (a) at low doses, this basic FSH isoform moderately increased FSH-induced cAMP production by cultured rat granulosa cells; (b) coincubation of the antagonist isoform with dibutyryl cAMP completely inhibited the effects of this cAMP analog on estrogen and tPA production; (c) the isoform was able to stimulate production of cAMP in a human fetal cell line expressing the recombinant human FSH receptor, and (d) the inhibitory effects of the isoform were not affected by staurosporine, a protein kinase C inhibitor. The effects of this isoform upon dibutyryl cAMP-induced estrogen and tPA production were blocked by the addition of a highly specific antibody directed against human FSH, further demonstrating that the antagonistic effects observed were due to FSH-like molecules. In contrast to the inhibitory effects exhibited by this basic FSH isoform, a more acidic FSH charge variant consistently acted as an agonist of pituitary and recombinant FSH on both estrogen production and induction of tPA enzyme activity. These results indicate that the anterior pituitary gland normally produces FSH isoforms which act as either agonists or antagonists of FSH at the target cell level.

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Section: Methodsmentioning

confidence: 99%

A Naturally Occurring Basically Charged Human Follicle-Stimulating Hormone (FSH) Variant Inhibits FSH-Induced Androgen Aromatization and Tissue-Type Plasminogen Activator Enzyme Activity in vitro

et al. 1998

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“…Cells were scraped with a rubber policeman and the content of wells belonging to the same incubation group pooled and processed for total RNA isolation as described below. (Bex & Corbin 1981). After separation of the protein-bound and free iodine-125 by Sephadex G-100 (Pharmacia) column chromatography, 125 I-labelled FSH was further purified by concanavalin A chromatography (Pharmacia) as described by Dufau et al (1972).…”

Section: Granulosa Cell Culture and In Vitro Bioassays Of Fshmentioning

confidence: 99%

Differential effects of the charge variants of human follicle-stimulating hormone

Timossi¹,

Barrios-De-Tomasi²,

González-Suárez³

et al. 2000

Journal of Endocrinology

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FSH is synthesized and secreted by the anterior pituitary gland in multiple molecular forms; the release of these isoforms depends on the endocrine status of the donor at the time of sample collection. In the present study, we analysed the possibility that the FSH charge isoforms may exert differential effects at the target cell. Seven FSH isoform mixes were isolated from pooled anterior pituitary glycoprotein extracts by high resolution chromatofocusing, followed by affinity chromatography, which removed nearly 90% of the LH that co-eluted with the FSH isoforms during chromatofocusing. The isoforms (isoform I, pH >7·10; II, pH range 6·60-6·20; III, pH 5·47-5·10; IV, pH 5·03-4·60; V, pH 4·76-4·12; VI, pH 4·05-3·82 and VII, pH <3·80) were then tested for their capacity to stimulate cAMP release, androgen aromatization and tissue-type plasminogen activator (tPA) enzyme activity and cytochrome P450 aromatase, tPA and inhibin -subunit mRNA production by rat granulosa cells in culture. cAMP and oestradiol production were determined by RIA, tPA enzyme activity by SDS-PAGE and zymography and all mRNAs by northern blot hybridization analysis and semiquantitative RT-PCR. All isoforms, with the exception of isoform I, stimulated synthesis and release of cAMP, oestrogen and tPA enzyme activity in a dosedependent manner; the potency of the less acidic isoforms (pH 6·60-4·60) was greater than that exhibited by the more acidic/sialylated analogs (pH 4·76 to <3·80; potencies II>III>IV>V>VII>VI). A similar trend was observed in terms of cytochrome P450 aromatase and tPA mRNA production. In contrast, when FSH-stimulated production of -inhibin mRNA was analysed, isoforms V-VII were significantly more potent (two-to threefold) than the less acidic/sialylated counterparts (II-IV). In contrast to isoforms II-VII (which behaved as FSH agonists), isoform I (elution pH >7·10) completely blocked P450 aromatase and tPA mRNA expression, without altering that of a constitutively expressed gene (glyceraldehyde-3-phosphate dehydrogenase). These results show for the first time that the naturally occurring human FSH isoforms may exhibit differential or even unique effects at the target cell level.

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“…These actions were initially felt to result from a sustained increase in gonadotropin levels, with subsequent reduction in ovarian gonadotropin receptors (8). However, studies in hypophysectomized animals have shown that GnRH also exerts a direct effect on the ovary (4,(9)(10)(11). GnRH inhibits steroidogenesis in isolated granulosa and luteal cells (9,12,13), and GnRH receptors have recently been identified in luteinized ovaries (14)(15)(16).…”

mentioning

confidence: 99%

Ovarian Gonadotropin-Releasing Hormone (GnRH) Receptors: Characterization, Distribution, and Induction by GnRH*

1981

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Gonadotropin-releasing hormone (GnRH) and its analogs have direct extrapituitary effects on the gonads to inhibit steroidogenesis. In the present study, the nondegradable GnRH analog [ 125 I]D-Ala a -des-Glyio-GnRH ethylamide is shown to specifically bind to ovarian, testicular, and adrenal membrane preparations. The ovarian GnRH receptor has a binding affinity similar to that of the anterior pituitary receptor and is specific for GnRH and GnRH analogs.The GnRH-binding capacity of whole ovarian membrane preparations is 150 fm/mg protein, 3-to 4-fold lower than that of anterior pituitary membranes. The number or affinity of receptors prepared from whole ovarian tissue is not influenced by the time of day, stage of the estrous cycle, or hypophysectomy. However, the GnRH receptor concentration is higher in follicular (371 ± 43 fmol/mg) than luteal (162 ± 25 fmol/mg) membranes from cycling rats.

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Luteinizing Hormone-Releasing Hormone (LHRH) and LHRH Agonist Termination of Pregnancy in Hypophysectomized Rats: Extrapituitary Site of Action*

Cited by 48 publications

References 32 publications

A Naturally Occurring Basically Charged Human Follicle-Stimulating Hormone (FSH) Variant Inhibits FSH-Induced Androgen Aromatization and Tissue-Type Plasminogen Activator Enzyme Activity in vitro

A Naturally Occurring Basically Charged Human Follicle-Stimulating Hormone (FSH) Variant Inhibits FSH-Induced Androgen Aromatization and Tissue-Type Plasminogen Activator Enzyme Activity in vitro

Differential effects of the charge variants of human follicle-stimulating hormone

Ovarian Gonadotropin-Releasing Hormone (GnRH) Receptors: Characterization, Distribution, and Induction by GnRH*

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