INHIBITION BY SOMATOMEDINS OF GROWTH-HORMONE SECRETION STIMULATED BY HYPOTHALAMIC GROWTH-HORMONE RELEASING-FACTOR (SOMATOCRININ GRF) OR THE SYNTHETIC PEPTIDE HPGRF

  • 1 January 1982
    • journal article
    • research article
    • Vol. 295  (11) , 651-654
Abstract
In the in vitro monolayer [rat] pituitary cell culture system, somatomedin- C and IGF-I [insulin-like growth factor] are practically equipotent to inhibit the secretion of growth hormone stimulated by hypothalamic growth hormone releasing factor (GRF) or the synthetic peptide hydroxyprolyl GRF-44 (3-200 .times. (3-200 .times. 10-12 M). Highly purified somatomedin-C or IGF-I are active to inhibit the effect of GRF at concentrations of 0.5 to 10 ng/ml (1.0 .times. 10-10 M - 1.3 .times. 10-9 M) in either short-term (3-4 h) or long-term (24 h) incubation, with no statistical difference between the results obtained in either duration of incubation. IGF-II is less potent than IGF-I as an inhibitor of GRF. The effect of the somatomedins is specific for the secretion of growth hormone and is not duplicated by other growth factors such as epidermal growth factor (EGF) or fibroblast growth factor (FGF).