Purification of canine gut glucagon-like immunoreactivity (GLI) and its insulin releasing activity

In order to clarify the nature of the biological action of gut glucagon-like immunoreactivity (GLI), GLI was extracted from the mucosa of the canine intestine and purified by gel filtration and affinity chromatography. 1500 gm of the mucosa yielded approximately 7 gm of crude extract of GLI. This crude extract was applied to a column packed with Sephadex G-50 or Bio-Gel P-10 and two peaks were obtained, Peak I and II. Each peak was purified with affinity chromatography, bound to gamma-globulin of anti-glucagon rabbit-serum. In this step, the GLI was purified approximately 80 times in comparison with the crude extract. Peak I or Peak II, as well as pancreatic glucagon, was infused successively into the pancreaticoduodenal artery of the anesthetized dogs. When buffer solution or the Peak I GLI was infused, the plasma immunoreactive insulin in the pancreatic vein did not change significantly. In contrast, both the Peak II and pancreatic glucagon promoted insulin secretion from the pancreas. The results obtained in this experiment demonstrate the promotion of insulin release from the pancreas and suggest an important role of gut GLI in the absorption and metabolic processing of nutrients.