Hormonal regulation of rat hypothalamic neuropeptide mRNAs: Effect of hypophysectomy and hormone replacement on growth-hormone-releasing factor, somatostatin and the insulin-like growth factors

Teresa L. Wood, Michael Berelowitz, Marie C. Gelato, Charles T. Roberts, Derek LeRoith, William J. Millard, Jeffrey F. McKelvy

    Research output: Contribution to journalArticle

    48 Scopus citations

    Abstract

    Hormonal feedback regulation of hypothalamic peptides putatively involved in growth hormone (GH) regulation has been studied by measurement of steady-state mRNA levels in male hypophysectomized rats with or without thyroid hormone. corticosterone, testosterone or GH replacement. Hypothalamic GH-releasing factor (GRF) mRNA levels increased progressively following hypophysectomy to 420% of sham levels after 15 days while hypothalamic insulin-like growth factor I (IGF-I) and insulin-like growth factor II (IGF-II) mRNA levels decreased to less than 40% of sham levels. Whole hypothalamic somatostatin mRNA levels were not significantly different from sham. One week of continuous GH infusion restored hypothalamic IGF-I mRNA to levels (95%) indistinguishable from those in sham-operated controls but had no effect on either IGF-II or GRF mRNA. Thyroid hormone, corticosterone and testosterone treatment without GH had no effect on the hypophysectomy-induced reduction of either IGF-I or IGF-II mRNA levels but reversed the elevation of GRF mRNA. We conclude that hypothalamic IGF-I may be involved in GH feedback regulation and thus may function as a hypothalamic modulator of GH. In contrast, IGF-II may be regulated by one of the pituitary trophic hormones but not by GH or the target hormones tested. Finally, hypothalamic GRF mRNA regulation appears to be complex and may include target hormone feedback.

    Original languageEnglish (US)
    Pages (from-to)298-305
    Number of pages8
    JournalNeuroendocrinology
    Volume53
    Issue number3
    DOIs
    StatePublished - Jan 1 1991

    Keywords

    • Growth hormone
    • Growth-hormone-releasing factor
    • Hypothalamus
    • Insulin-like growth factor I
    • Insulin-like growth factor II
    • MRNA regulation
    • Rat
    • Somatostatin

    ASJC Scopus subject areas

    • Endocrinology, Diabetes and Metabolism
    • Endocrinology
    • Endocrine and Autonomic Systems
    • Cellular and Molecular Neuroscience

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