Differences in Extracellular Calcium Involvement Mediating the Secretion of Gonadotropin and Growth Hormone Stimulated by Two Closely Related Endogenous GnRH Peptides in Goldfish Pituitary Cells
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Résumé
Two endogenous gonadotropin-releasing hormone (GnRH) peptides, salmon GnRH (sGnRH) and chicken GnRH II (cGnRH II), stimulate gonadotropin (GtH) and growth hormone (GH) secretion in the goldfish. The extracellular calcium (e-Ca2+) dependence of the GtH and GH response to the two GnRH peptides were compared using static incubations of dispersed goldfish pituitary cells. Incubation with Ca(2+)-depleted medium (without the addition of Ca2+ salts and in the presence of EGTA) did not alter basal GtH secretion, but reduced the GtH response to sGnRH, and abolished the cGnRH II-induced GtH release. Blockade of e-Ca2+ entry by low concentrations of CoCl2 had no effect on basal GtH secretion but reduced cGnRH II and sGnRH stimulated GtH release when applied at 0.1 and 0.5 mM concentrations, respectively. In general, treatments with voltage-sensitive Ca2+ channel (VSCC) antagonists, verapamil, nifedipine and nicardipine, did not alter basal GtH release but attenuated GnRH-stimulated GtH responses. cGnRH II-induced GtH release was decreased by 10 nM verapamil and 1 nM nifedipine, whereas the reduction of GtH responses to sGnRH required 100 times higher concentrations of these VSCC antagonists. cGnRH II but not sGnRH stimulation of GtH secretion was also abolished by 10 microM nicardipine. In contrast to GtH release, exposure to Ca(2+)-depleted medium reduced basal GH release and abolished the GH responses to both GnRH peptides. sGnRH and cGnRH II-stimulated GH responses were both abolished by 0.1 mM CoCl2, decreased by 1 nM verapamil, and reduced by 10 nM nicardipine. Addition of 0.1 and 10 microM nifedipine inhibited the GH responses to sGnRH and cGnRH II, respectively. Basal GH release was not affected by the VSCC antagonists tested. Results from this study indicate that entry of e-Ca2+, in part through VSCC, is involved in GnRH stimulation of GtH and GH release from goldfish gonadotropes and somatotropes; however, the e-Ca2+ dependence of the GtH and GH responses to the two endogenous GnRHs differ. The stimulatory effects of cGnRH II on GtH secretion is more dependent on and sensitive to e-Ca2+ than sGnRH. Whereas the sensitivity of GH responses to manipulations of e-Ca2+ availability is, in most instances, similar for both GnRH peptides. These results further suggest that basal secretion of GH is more sensitive to e-Ca2+ than basal GtH release; however, VSCC are not involved in the maintenance of basal release of either hormone.
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Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,001 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,001 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découle