Neuroendocrine regulation of thyroid-stimulating hormone secretion in amphibians

Reiko Okada*, Tetsuya Kobayashi, Kazutoshi Yamamoto, Takashi Nakakura, Shigeyasu Tanaka, Hubert Vaudry, Sakae Kikuyama


    研究成果: Conference contribution

    29 被引用数 (Scopus)


    The hypothalamic peptides thyrotropin-releasing hormone (TRH), gonadotropin-releasing hormone (GnRH), and corticotropin-releasing factor (CRF), which have been postulated as acting as thyroid-stimulating hormone (TSH)-releasing hormone in amphibians, were tested for their activity by employing a recently developed radioimmunoassay for bullfrog (Rana catesbeiana) TSH. CRF markedly stimulated the release of TSH from both adult and larval bullfrog pituitary cells. Both TRH and GnRH moderately stimulated the release of TSH from adult pituitary cells but not from larval ones. The release of TSH was also enhanced by bullfrog hypothalamic extracts. The hypothalamic extract-evoked release of TSH was markedly reduced by a CRF receptor antagonist, suggesting that CRF and/or CRF-related peptides are the main TSH-releasing factors occurring in the bullfrog hypothalamus. Experiments using CRF receptor agonists and antagonists revealed that CRF acts through the type 2 receptor. With regard to other hypothalamic substances that influence the release of TSH, pituitary adenylate cyclase-activating polypeptide and vasoactive intestinal polypeptide were found to be potent stimulators and somatostatin an inhibitor of TSH release. Thus, it becomes clear that the main regulatory peptides controlling TSH secretion in amphibians are different from those in mammals. Triiodothyronine did not affect the basal release of TSH from the pituitary of either larval or adult bullfrogs but suppressed the CRF-induced release of TSH, suggesting that negative feedback by thyroid hormone is functioning both in larvae and adults.

    ホスト出版物のタイトルAnnals of the New York Academy of Sciences
    出版ステータスPublished - 2009 4月


    名前Annals of the New York Academy of Sciences

    ASJC Scopus subject areas

    • 生化学、遺伝学、分子生物学(全般)


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