Absence of true pancreatic glucagon but persistence of circulating pancreatic glucagon-like immunoreactivity after pancreatectomy in pigs

Abstract

The possible existence of circulating pancreatic type glucagon (immunoreactive glucagon as measured with a highly specific antibody) of extrapancreatic origin was investigated in 20-25 kg pigs after pancreatectomy. In intact conscious animals intravenous arginine infusions stimulated glucagon as well as insulin secretion, while blood glucose remained unaffected. Two weeks after pancreatectomy, and 48 hours after insulin withdrawal, basal glucagon and glucose concentrations were elevated (from 22 +/- 3.7 to 55 +/- 9.5 pmol/1 and 5.8 +/- 0.4 to 16.2 +/- 2.0 mmol/l, respectively), (mean +/- SEM), while insulin concentrations were either undetectable or very low. After pancreatectomy, however, glucagon concentrations no longer increased during arginine infusion. Gut type glucagon levels were not affected by pancreatectomy, and did not change during arginine infusion. When examined by gel filtration, plasma from unoperated pigs contained two components of pancreatic type glucagon, one coeluting with the glucagon marker, the other eluting earlier, probably reflecting larger molecular size. After pancreatectomy only this larger component was found in the plasma. The role of this component in the control of blood glucose is unknown.