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Differential In Vitro Secretion of Gonadotropin‐Releasing Hormone (GnRH) and [Hydroxyproline 9 ]GnRH from the Rat Hypothalamus During Postnatal Development
Author(s) -
Rochdi L.,
Théraulaz L.,
Enjalbert A.,
Gautron J.P.
Publication year - 2000
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1046/j.1365-2826.2000.00538.x
Subject(s) - medicine , endocrinology , forskolin , hypothalamus , gonadotropin releasing hormone , stimulation , biology , hormone , basal (medicine) , gonadotropin , chemistry , luteinizing hormone , insulin
The differential secretion of gonadotropin‐releasing hormone (GnRH) and [hydroxyproline 9 ]GnRH (HypGnRH) has been recently reported from the adult rat hypothalamus. We report here in vitro cosecretion of HypGnRH and GnRH by the hypothalamus of 2–45 day‐old‐rats and provide evidence that they are differentially regulated throughout development. The secretion of both forms of GnRH was increased in a dependent manner during depolarization by high K + solutions, and was stimulated by forskolin and 12‐ O ‐tetradecanoylphorbol‐13‐acetate (TPA), activators of adenylate cyclase and protein kinase C pathways, respectively. The proportion of HypGnRH in the release of GnRH‐like peptides remained stable and high (33–40%) under basal and K + ‐induced conditions until days 13 and 21, respectively. By contrast, the proportion of HypGnRH in the total GnRH‐like content of the developing hypothalamus continuously decreased (from 37% to 14%). Similarly, the proportion of HypGnRH: total GnRH‐like material released remained stable in TPA‐ (30%) and forskolin‐ (50%) induced secretion until postnatal day 8. Evaluation of release over tissue store ratios revealed a 1.3‐to 2.8‐fold higher release of HypGnRH compared to GnRH according to the different secretions and postnatal periods examined. The preferential recruitment of HypGnRH was maintained under basal and K + conditions during postnatal development, but it disappeared under TPA stimulation from day 13 onwards. After forskolin stimulation, the preferential mobilization of HypGnRH was markedly reduced from day 2 to day 13 but recovered its high perinatal level during puberty. Taken together, our results support the hypothesis that HypGnRH may play a specific role in development. In addition, a specific function of this peptide taking place during puberty through the activation of the adenylate cyclase pathway is suggested.