Portal and peripheral vein concentrations of insulin and glucagon after arginine infusion in morbidly obese subjects

Five morbidly obese subjects with fasting normoglycemia underwent catheterization of portal and peripheral veins immediately prior to jejunoileal bypass surgery. Levels of immunoreactive insulin (IRI), immunoreactive glucagon (IRG), and glucose were determined in simultaneously obtained serum samples before and after infusion of arginine. Portal levels exceeded peripheral levels by at least 50% with IRI and by 30%–40% with IRG. These results were similar to those reported in nonobese subjects and show that in morbid obesity as well as in nonobese states, peripheral insulin to glucagon molar ratios ($\text{I}\text{G}$) underestimate portal $\text{I}\text{G}$. Although hepatic extraction was not specifically measured, the data suggest that the peripheral levels of insulin and glucagon reported in morbid obesity result from alterations in secretion and not altered extraction.