Portal and Peripheral Vein Immunoreactive Glucagon Concentrations After Arginine or Glucose Infusions

Catheterization of the portal vein via the umbilical vein was performed under local anesthesia in eight nondiabetic subjects before exploratory laparotomy for a variety of conditions. Levels of immunoreactive glucagon (IRG) and immunoreactive insulin (IRI) were determined in simultaneously obtained portal and peripheral vein plasma before, during and after a fifteen minute arginine infusion (30 gm.) in five subjects. The mean portal vein to peripheral vein glucagon ratio in the postabsorptive state was 1.7 ± 0.5. A biphasic portal vein IRG response to arginine was observed, with the initial glucagon peak occurring within one minute of the beginning of the infusion. Peripheral IRG concentrations did not reflect the biphasic response. The portal vein IRI response to arginine was also mildly biphasic, and the first phase occurred before a detectable increase in blood glucose. The portal vein IRG peak either preceded or coincided temporally with the portal vein IRI peak. In three nondiabetic subjects, portal vein IRG decreased rapidly to its nadir within two minutes after a two minute glucose infusion (25 gm.) was started.