Concentrations of Glucagon and the Insulin: Glucagon Ratio in the Portal and Peripheral Circulation

SummaryIn postoperative patients studied in the postabsorptive state by mean of an umbilical vein catheter, concentrations of glucagon and insulin in portal blood exceeded those in peripheral venous blood. However, the portal—peripheral gradient for insulin (1.8-4.0) was consistently greater than that observed for glucagon (1.1-1.5). Consequently, the insulin:glucagon (I/G) molar ratio in the portal vein was 100% higher than in peripheral blood. A direct linear correlation however, was observed between portal and peripheral I/G molar ratios. The data indicate that peripheral measurements underestimate the absolute ratio of insulin to glucagon in portal blood, but nevertheless provide an index of relative hormonal availability in the hepatic circulation.