AJP - Endocrinology and Metabolism, Vol 255, Issue 6 E829-E832, Copyright © 1988 by American Physiological Society
GHRF causes biphasic stimulation of SRIF secretion from rat hypothalamic cells
S. Richardson, S. Twente and T. Audhya
Department of Medicine, Veterans Administration Medical Center, New York, New York.
The complex interactions of the hypothalamic releasing peptides
somatostatin (SRIF) and growth hormone (GH)-releasing hormone (GHRF), which
regulate GH secretion, are still incompletely understood. To further
scrutinize these interactions, we have studied the effects of GHRF on SRIF
secretion from dispersed adult rat hypothalamic cells. Rat GHRF caused
calcium- and dose-dependent stimulation of SRIF release in static 1-h
incubations. SRIF release was stimulated by GHRF in a concentration range
of 1-100 nM. However, the extended dose-response curve was biphasic in
nature, with a significantly lower SRIF response in the presence of 1
microM GHRF vs. 100 nM GHRF. SRIF release, stimulated by another
secretagogue (10 microM veratridine), was not affected by the presence or
absence of 1 microM GHRF, suggesting the lack of toxic impairment of
hypothalamic cell function by GHRF at this concentration. In conclusion, a
biphasic stimulatory pattern of SRIF secretion in response to GHRF was
observed in experiments employing dispersed rat hypothalamic cells. The
biphasic SRIF response pattern to GHRF may be relevant in the physiological
regulation of GH secretion.
