[Effect of peptide hormone fragments and thyroliberin on mouse blood glucose homeostasis]

The comparative effects of thyroliberin (TRH), pentagastrin, C-terminal tripeptides of gastrin (MNF), luliberin (RPG) and its analog (RPF), oxytocin (PLG) and N-terminal tripeptide of angiotensin (NRV) on the glucose concentration in mouse blood, as well as the interrelationship between the peptides under study and insulin and somatostatin, were studied. It was found that all the peptides (except PLG) at doses 5, 50 and 100 mg/kg (intraperitoneally) exert a hypoglycemic effect comparable to that of insulin at the dose of 0,15 MU/kg (subcutaneously). The dose-dependent effect is observed only in the case of TRH. Somatostatin reverses the hypoglycemic action of TRH, MNF and NRV. TRH and RPF decrease the glucose-induced rise in insulin concentration measured by RIA. The structure-activity relationship and possibility of the formation of endogenous peptide hormone fragments as products of hormone molecules enzymatic cleavage and their glucoregulatory role are discussed.