Effect of C-terminal chain shortening on the insulin-antagonistic activity of human growth hormone 177–191

Abstract

Abstract. Six synthetic C-terminal shortened fragments of the reduced and S-carbamidomethylated peptide corresponding to residues 177 to 191 of human growth hormone (Cam-hGH 177–191) were assayed for insulin antagonistic activity in vivo. Two of the peptides, CamhGH 177–191 and cam-hGH 177–191 were, in nanomolar quantities, both active in that they caused significant hyperglycaemia and insulin resistance in normal rats. The remaining peptides, hGH 177–180, Cam-hGH 177–185, Cam-hGH 177–187 and hGH 177–189 were all inactive even at up to one hundred times the dose employed for the active peptides. The results indicate that an insulin antagonistic core of hGH is contained within amino acid residues 178 to 190 inclusive.