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Stress-Related Changes in β-Endorphin Processing: The Limitations of Slaughterhouse Material
Authors:A. Ian Smith  Catherine A. Wallace  Lain J. Clarke  John W. Funder
Affiliation:Medical Research Centre, Prince Henry's Hospital, Melbourne, Australia 3004.
Abstract:
In the sheep, unlike many other species, a significant proportion (>25%) of immunoreactive β-endorphin in the anterior pituitary is post-translationally modified to opioid-inactive, α-N-acetylated forms. In a study to determine the precise molecular nature of α-N-acetylated β-endorphin immunoreactivity, we noted a striking difference in high-performance liquid chromatography profiles of anterior pituitary extracts between sheep killed on the farm, and age-, sex- and strain-matched slaughterhouse animals. These altered patterns of a-N-acetylated β-endorphin processing were reproduced in farm animals by chronic (≤ 4 days) treatment with the synthetic glucocorticoid dexamethasone; in contrast dexamethasone had no effect on a-N-acetylated β-endorphin processing in hypothalamo-pituitary disconnected sheep. These data suggest that (1) the change in processing is a stress response, mediated by prolonged glucocorticoid exposure, (2) this effect is central, rather than a direct effect on the pituitary, and (3) the relative abundance of various peptide sequences in slaughterhouse-derived material may not reflect their abundance under more physiological conditions.
Keywords:α-N-acetylation    β-endorphin    anterior pituitary    stress    glucocorticoids
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