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

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Abstract
SUMMARY: 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 μg/kg/h alone produced a peak GH response of 27·0 ± 7·6 mU/1 (mean ± SEM). Somatostatin 1·0 μg/kg/h markedly inhibited the GH response to hpGRF 1–44 with mean levels > 4·0 mU/1 during the infusion, though a rebound rise in GH levels to 26·1 ± 9·0 mU/1 was observed at the end of the infusion period. Somatostatin 0·2 μg/kg/h inhibited the GH response to hpGRF 1–44 to a lesser degree (peak GH during the infusion 11·7 ± 2·5 mU/1) and the rebound rise in GH levels (maximum 13·2 ± 4·3 mU/1) was less than that observed with high dose somatostatin. During somatostatin 1·0 μg/kg/h alone GH levels were suppressed > 1·0 mU/1 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.