THE INTERACTION OF HUMAN PANCREATIC GROWTH HORMONE RELEASING FACTOR 1–44 WITH SOMATOSTATIN IN VIVO IN NORMAL MAN

Abstract

The interaction between the stimulatory effects of hpGRF 1-44 and the inhibitory effects of somatostatin on GH release have been investigated in six normal male subjects receiving continuous 4 h infusions of these peptides alone and in combination. hpGRF 1-44 0.3 .mu.g/kg per h alone produced a peak GH response of 27.0 .+-. 7.6 mU/l (mean .+-. SEM). Somatostatin 1.0 .mu.g/kg per h markedly inhibited the GH response to hpGRF 1-44 with mean levels < 4.0 mU/l during the infusion, though a rebound rise in GH levels to 26.1 .+-. 9.0 mU/l was observed at the end of the infusion period. Somatostatin 0.2 .mu.g/kg per h inhibited the GH response to hpGRF 1-44 to a lesser degree (peak GH during the infusion 11.7 .+-. 2.5 mU/l) and the rebound rise in GH levels (maximum 13.2 .+-. 4.3 mU/l) was less than that observed with high dose somatostatin. During somatostatin 1.0 .mu.g/kg per h alone GH levels were suppressed < 1.0 mU/l followed by a rebound at the end of the infusion in only two subjects. These data demonstrate a dose-dependent inhibition of hpGRF 1-44 by somatostatin in vivo in man.