The hypophysiotropic activities of a synthetic human pancreatic growth hormone releasing factor (hpGRF) with 40 residues was examined in vitro using rat pituitary halves. At concentrations from 10-10 M to 10-7 M the peptide stimulated GH release in a dose-dependent manner with the ED50 being 1.2×10-9 M. The concentration of 10-10 M hpGRF is comparable to the basal hypophyseal portal blood levels of other known hypothalamic hypophysiotropic hormones. However, GH release was enhanced three-fold by concentration as low as 10-12 M, though no dose-response relationship was observed up to 10-10 M. Thus, this peptide not only stimulates the release of GH in a dose-dependent manner, but at lower concentrations also maintains elevated GH levels. The release of ACTH, β-endorphin, LH, and FSH was not affected by hpGRF at any of the concentrations tested. At hpGRF concentrations less than 10-7 M, the release of TSH and PRL were unaffected. However, at 10-6 M, TSH release was enhanced about 2.5 fold and prolactin release was elevated slightly.
- GH Pituitary hormones
- Growth hormone releasing factor (GRF)
- In vitro test
- Rat pituitary
ASJC Scopus subject areas
- Cellular and Molecular Neuroscience