Somatostatin secretion and action in the regulation of growth hormone secretion.
The inhibition of growth hormone (GH) secretion by the hypothalamic peptide, somatostatin, is mediated by two critical factors: the concentration of the peptide in hypothalamic portal plasma and the number of somatostatin (SRIF) receptors on the somatotroph. The secretory patterns of SRIF and GH-releasing hormone (GRH) in portal blood of unanesthetized sheep is pulsatile and a close relationship of GRH pulses to those of GH secretion was documented, while those of SRIF appear to have more of a modulatory role on the responses to GRH. Peripheral infusion of SRIF at a rate to provide concentrations comparable to those in the portal system leads to a desensitization of SRIF effects on the somatotroph, likely mediated by down-regulation of SRIF receptors. These effects are believed to modulate the GH responses to GRH secretion in the generation of pulsatile GH secretion.
Frohman
L A
LA
Division of Endocrinology and Medicine, University of Cincinnati College of Medicine, OH 45267.
Downs
T R
TR
Kelijman
M
M
Clarke
I J
IJ
Thomas
G
G
D000818:Animals; D013006:Growth Hormone / Q000378:metabolism*; D006801:Humans; D013004:Somatostatin / Q000378:metabolism* / Q000502:physiology
D013004:Somatostatin; D013006:Growth Hormone