Publication: Recruiting of somatotroph cells
after combined somatostatin, GHRH and
growth hormone (GH) secretagogue stimulation in a
study of pituitary GH reserve in prepuberal female rats
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Date
2006
Authors
Jiménez Reina, L. ; García-Martínez, E. ; Rojas, J.P. ; Cañete, M.D. ; Bernal, G. ; Cañete, R.
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Publisher
Murcia : F. Hernández
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DOI
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info:eu-repo/semantics/article
Description
Abstract
Diagnostic confirmation of growth hormone
(GH) deficiency in children and adults is based on
stimulation tests designed to assess the pituitary reserve
by measuring the amount of GH released into the
bloodstream; however, the results obtained by this
means cannot provide any direct indication of the
amount of GH actually produced by pituitary
somatotroph cells. The present paper sought to test the
hypothesis that release of GH following administration
of specific stimuli does not accurately reflect the
somatotroph cell response, and that the amount of GH
released into the bloodstream may often be greater or
smaller than the amount synthesized. GH release and
changes in the proportion of somatotroph cells were
charted in prepuberal female Wistar rats, following
administration of several different GH stimuli: GHRH (1
µg/kg), GHRP-6 (1 µg/kg), GHRELIN (1 µg/kg) and
combined GHRH-based treatments, with or without
SRIH pretreatment (1 µg/kg) 90 minutes earlier. Peak
serum GH values were recorded 15 minutes after
administration of GHRH+GHRELIN and
GHRH+GHRP-6; maximum stimulation in terms of an
increased proportion of somatotroph cells occurred 15
minutes after combined adminstration of GHRH +
GHRELIN. SRIH pretreatment (- 90 min) inhibited GH
release, with a subsequent "escape" and lack of response
to stimulation which lasted at least 30 minutes except
following administration of GHRH. However, combined
administration of GHRH+GHRELIN maintained
stimulation of the somatotroph cell population. In
conclusion, the results suggest that the enhanced GH
release prompted by stimulation tests used to diagnose
GH deficiency in prepuberal female rats does not fully reflect somatroph cell dynamics, and that not all the GH
produced and stored by somatotroph cells is released
into the bloodstream.
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