Hyperglycemic action of synthetic C-terminal fragments of human growth hormone.

The synthetic peptides corresponding to amino acids 172-191, 176-191, 177-191, 178-191, 179-191, and 180-191 of human growth hormone (hGH) have been studied for their in vivo effects in normal rats. Four of the peptides (hGH 172-191, 176-191, 177-191, and 178-191) produced a short-lived rise in blood glucose and a more sustained rise in plasma insulin, whereas the other two (hGH 179-191 and 180-191) were inert in the systems tested. A single dose (5 nmol/kg body wt) of the peptides containing the amino acids sequence 178-191 of the hGH molecule significantly reduced insulin sensitivity of the animals in intravenous insulin tolerance tests. The findings also indicate that the biologically active peptides must not only have the minimum of the informational sequence but also that this must be in correct physical configuration.