The effects of cysteamine on thyrotropin and immunoreactive β-endorphin secretion in the rat

William J. Millard, Stephen M. Sagar, Thomas M. Badger, Daniel B. Carr, Michael A. Arnold, Eliot Spindel, Norman W. Kasting, Joseph B. Martin

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    Abstract

    We examined the effects of the thiol agent cysteamine (CSH), which is known to deplete the hypothalamus of immunoreactive somatostatin, on physiological TSH and β-endorphin secretion in the adult male rat. CSH at doses of 90 and 300 mg/kg CSH produced a rapid decline in plasma TSH, whereas a dose of 30 mg/kg did not alter plasma TSH levels. After the higher doses of CSH, TSH levels in the blood remained lower than control values on day 2, but returned to normal by 1 week. This decrease in TSH within the plasma was not associated with a reduction in hypothalamic TRH concentrations. The TSH response to 500 ng/kg TRH was normal in CSH-treated animals. Blockade of norepinephrine synthesis with diethyldithiocarbamate (500 mg/kg) or fusaric acid (100 mg/kg) inhibited TSH secretion in a manner similar to that of CSH. β-Endorphin-like immunoreactivity (β-End-LI) was elevated in the plasma immediately after CSH (300 mg/kg) administration. This was associated with a 58% reduction in anterior pituitary β-End-LI and no change in hypothalmic β-End-LI. Plasma β-End-LI returned to normal on day 2. The increase in plasma β-End-LI induced by immobilization stress was not compromised by CSH treatment. The observed effects of CSH on both TSH and β-End-LI are consistent with a reduction in central norepinephrine neurotransmission through the known action of CSH to inhibit dopamine-β -hydroxylase. Acute stress may play a role as well in the observed changes in TSH and β-End-LI secretion.

    Original languageEnglish (US)
    Pages (from-to)518-525
    Number of pages8
    JournalEndocrinology
    Volume112
    Issue number2
    DOIs
    StatePublished - Feb 1983

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    ASJC Scopus subject areas

    • Endocrinology

    Cite this

    Millard, W. J., Sagar, S. M., Badger, T. M., Carr, D. B., Arnold, M. A., Spindel, E., Kasting, N. W., & Martin, J. B. (1983). The effects of cysteamine on thyrotropin and immunoreactive β-endorphin secretion in the rat. Endocrinology, 112(2), 518-525. https://doi.org/10.1210/endo-112-2-518