pGlutamylglutamylprolineamide modulation of growth hormone secretion in domestic fowl: antagonism of thyrotrophin-releasing hormone action?

in Journal of Endocrinology
Authors:
S. Harvey
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,
V. L. Trudeau
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R. J. Ashworth
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, and
S. M. Cockle
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DOI:
https://doi.org/10.1677/joe.0.1380137
Volume/Issue:
Volume 138: Issue 1
Article Type:
Research Article
Page Range:
137–147
Online Publication Date:
Jul 1993
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ABSTRACT

Pyroglutamylglutamylprolineamide (pGlu-Glu-ProNH2) is a tripeptide with structural and immunological similarities to thyrotrophin-releasing hormone (TRH; pGlu-His-ProNH2). Since TRH stimulates GH secretion in domestic fowl, the possibility that pGlu-Glu-ProNH2 may also provoke GH release was investigated. Unlike TRH, pGlu-Glu-ProNH2 alone had no effect on GH release from incubated chicken pituitary glands and did not down-regulate pituitary TRH receptors. However, pGlu-Glu-ProNH2 suppressed TRH-induced GH release from pituitary glands incubated in vitro and competitively displaced [3H]methyl3-histidine2-TRH from pituitary membranes. Systemic injections of pGlu-Glu-ProNH2 had no significant effect on basal GH concentrations in conscious birds, but promptly lowered circulating GH levels in sodiumpentobarbitone anaesthetized fowl. Submaximal GH responses of conscious and anaesthetized birds to systemic TRH challenge were, however, potentiated by prior or concomitant administration of pGlu-Glu-ProNH2. These results demonstrate, for the first time, that pGlu-Glu-ProNH2 has biological activity, with inhibitory and stimulatory actions within the avian hypothalamo-pituitary axis. These results indicate that pGlu-Glu-ProNH2 may act as a TRH receptor antagonist within this axis.

Journal of Endocrinology (1993) 138, 137–147

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Print ISSN:
0022-0795
Online ISSN:
1479-6805
Page(s):
11
Article Type:
Research Article
Print Publication Date:
01 Jan 1993
Online Publication Date:
Jul 1993