Biphasic Pattern of Follicle Stimulating and Luteinizing Hormone Responses to Gonadotropin-Releasing Hormone in vitro

Leblanc, Pierre; Pattou, E.; I’Heritier, Andrée; Gogan, F.; Slama, A.; Kordon, C.

doi:10.1159/000123442

Cited by 5 publications

(3 citation statements)

References 19 publications

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“…Specific activity was close to 2.000 Ci/mmol. The nonradioactive peptide content of the preparation was negligible when measured by radioimmunoassay [16] using an antibody raised against the N-terminal fragment of the GnRH molecule [17], The maximum binding capacity to an excess of pituitary membrane preparation was 30%.…”

Section: Quantitative Auloradiographvmentioning

confidence: 97%

Characterization and Distribution of Receptors for Gonadotropin-Releasing Hormone in the Rat Hippocampus

et al. 1988

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Distribution and properties of receptors for gonadotropin-releasing hormone (GnRH) were analyzed in the brain of adult male rats. Binding of the iodinated GnRH agonist Des-Gly¹⁰-(D-Ala⁶)-GnRH ethylamide was studied in hippocampus and anterior pituitary using three convergent approaches: quantitative autoradiography on frozen tissue, binding to fresh slices, and binding to crude membrane preparations. In all cases, binding was specific, saturable, and time, pH, and temperature dependent. Quantitative autoradiography revealed that the density of binding sites was high in the stratum oriens and stratum radiatum of the CA1-CA4 regions of Ammon’s horn. The pyramidal cell layer was faintly labelled. Binding was almost undetectable in the dentate gyrus. The highest density of sites (B_max = 11.6 + 1.0 fmol/mg protein) was observed in the stratum radiatum of the CA3 region. Under the same conditions the value obtained for pituitary tissues was 20.7 + 2.8 fmol/mg protein. Analysis of saturation curves indicated only one class of high-affinity sites for the hippocampus (CA₃; K_d = 0.28 + 0.03 nM) and for the pituitary (K_d = 0.29 ± 0.08 nM). Both native GnRH and GnRH antagonist were potent competitors of binding. Fresh slices and membrane preparations from whole hippocampus confirmed these autoradiographic data and yielded affinity constants of 0.28 + 0.01 and 0.52 + 0.08 nM, respectively. In addition, a very high binding density was present in the amygdaloid complex, while binding was barely detectable in the hypothalamus. These results demonstrate that high densities of specific GnRH receptors are present in areas concerned with the regulation of behavioral functions. GnRH may thus be involved as a neurotransmitter in the integration of endocrine and behavioral reproductive processes.

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Section: Quantitative Auloradiographvmentioning

confidence: 97%

Characterization and Distribution of Receptors for Gonadotropin-Releasing Hormone in the Rat Hippocampus

et al. 1988

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“…By calculation of the release rate, Koninckx et al (1976) showed a biphasic FSH release in women. Consistent with this finding in vitro experiments have demonstrated a clear biphasic FSH release pattern with a time course almost similar to that of LH {Eddie et al 1982;Jenner, de Koning and van Rees 1982;Leblanc, Pattou, VHeritier, Gogan, Slama and Kordon 1983;Waring and Turgeon 1983). Our in vivo study also demonstrates a biphasic FSH response (in both eugonadal and oligospermic men).…”

Section: Discussionmentioning

confidence: 60%

Effects of Continuous LHRH Infusion on Plasma Levels of LH and FSH in Males, Before and After Oestrogen or Anti-Oestrogen Treatment

Bergeijk¹,

Gooren²,

Kessel³

et al. 1986

Horm Metab Res

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In order to study the role of oestrogens on gonadotrophin release in the human male, LHRH was administered as an infusion at a constant rate of 0.5 micrograms/minute for 4 hours to 7 normogonadotrophic oligozoospermic men, 6 eugonadal male-to-female transsexuals and 9 eugonadal male volunteers. In agreement with in vitro data a biphasic release pattern of both LH and FSH was observed in eugonadal transsexuals as well as in normogonadotrophic oligozoospermic men. In the latter the release of LH was greater than in eugonadal transsexual males and volunteers, which points to a different functioning of the hypothalamic-pituitary unit in normogonadotrophic oligozoospermic men. On the other hand the FSH response to LHRH stimulation was normal in these men. Three months' treatment with the oestrogen-receptor antagonist tamoxifen (TAM) (10 mg twice daily) in the normogonadotrophic oligozoospermic men stimulated basal LH, FSH and testosterone (T) levels. The fact that gonadotrophin levels rose in spite of increased T levels, suggests a role of endogenous oestrogens in the negative feedback regulation of gonadotrophin release in these men. Upon TAM treatment the first phase, the plateau and the second phase of LH release were augmented, whereas only the plateau and the second phase of FSH release were increased. Six weeks' administration of the oestrogen ethinyloestradiol (EE) (10 micrograms three times a day) in the eugonadal transsexual males suppressed basal T and oestradiol (E2) levels without affecting basal gonadotrophin levels significantly. In EE-treated males the first phase of LH release tended to be lower, whereas the plateau of LH had decreased significantly. The second phase of LH was unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)

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“…The iodination mixture was applied to a (0.9 x 10 cm) column, and eluted with increasing molarity of acetic acid; 1 ml fractions were collected. Unlabelled hormone was assayed in an RIA using an antibody raised against the N-terminal fragment of GnRH (41). It was readily eluted by 1.75 mM acetic acid, whereas labelled GnRH was eluted in two peaks at higher acetic acid concentrations (8 mM).…”

Section: Ligand Iodinationmentioning

confidence: 99%

Temperature and Protein Kinase C Modulation of Gonadotropin‐Releasing Hormone Receptors in Pituitary Cells from Intact or Castrated Male Rats

Leblanc

I’Heritier

Mounier

et al. 1990

J Neuroendocrinology

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Unite de recherches sur la dynamique des ensembles neuroendocriniens, U 159 INSERM, 2ter rue d'AIesia, 75014 Paris, France.t Pharmacologie Neuro-lmmuno-Endocrinienne (CNRS UA 11 13), lnstitut Pasteur, 28 rue du Dr Roux, 75015 Paris, France.Key words: gonadotropin-releasing hormone receptors, protein kinase C, pituitary cell culture, castration. AbstractBinding constants of ['251]Des-Gly,0-(D-Ala,)-gonadotropin-releasing hormone-ethylamide (GnRHa) to dispersed pituitary cells were evaluated in a 4-day culture. Cells were sampled either from intact or from castrated male rats and binding was measured at various temperatures before or after treatment with phorbol-12-myristate-13-acetate (PMA) or l-5-(isoquinolinyl-sulfc.xyl) 2-methylpiperazine (H7), which activate or inhibit, respectively, protein kinase C (PKC). In cells from intact rats incubated with increasing concentrations of ligand at 21 "C for 25 rnin, the Scatchard plot was not linear and calculation of the Hill coefficient (NH) was indicative of positive cooperativity (NH= 1.26_+0.02). Such non-linearity was not observed when cells were incubated at 0.5 "C for 3 h. In that condition the maximal number of binding sites measured at equilibrium (Bmax) increased (15.1 t0.05 versus 9.3k0.5 fmoles x mg-' proteins at 21 "C). Two control experiments permitted us to rule out the possibility that lower B , , , at 21 "C might reflect internalization: 1) Cells were first incubated with the ligand at 21 "C for 25 min and subsequently for 3 additional hours at 0.5 "C. Preincubation did not affect the B , , , obtained at 0.5 "C; 2) when the radioligand bound to the cell surface was washed out with an acidic buffer, only 13% of the specific radioactivity was retained irrespective of the ligand concentration applied, a much lower value than the 40% binding difference observed between 05°C and 21°C. When the cells were incubated with PMA, the Scatchard plot was linearized and the B, , , recorded at 21 "C increased by 50% over control cells (13k0.7 fmolesxrng-' proteins). Conversely, inhibition of PKC by H7, a preferential PKC inhibitor, was ineffective. In contrast, cells sampled from castrates exhibited linear and comparable Scatchard plots at either 0.5 or 21 "C, with B , , , values of 14.4k0.3 and 15k0.34 fmoles x mg-' proteins, respectively. PKC activation did not affect binding in that model, but H7 decreased the number of sites (B,,,= 10.7t0.9) and induced appearance of positive cooperativity (NH= 1.36k0.07). Taken together, these experiments reveal a pool of GnRH receptors in the pituitary of intact rats that recognizes the ligand in a phosphorylation-dependent manner. These binding sites also became evident when biological properties of the membrane were modified by temperature or cell homogenization. After castration, PKC activation was no longer a prerequisite for recruitment of the total population of receptors whereas protein kinase inhibition resulted in a reduction of maximal binding. Finally, our observations demonstrate that GnRH binding can exhibit positiv...

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Biphasic Pattern of Follicle Stimulating and Luteinizing Hormone Responses to Gonadotropin-Releasing Hormone in vitro

Cited by 5 publications

References 19 publications

Characterization and Distribution of Receptors for Gonadotropin-Releasing Hormone in the Rat Hippocampus

Characterization and Distribution of Receptors for Gonadotropin-Releasing Hormone in the Rat Hippocampus

Effects of Continuous LHRH Infusion on Plasma Levels of LH and FSH in Males, Before and After Oestrogen or Anti-Oestrogen Treatment

Temperature and Protein Kinase C Modulation of Gonadotropin‐Releasing Hormone Receptors in Pituitary Cells from Intact or Castrated Male Rats

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