EFFECT OF HEPATIC PORTAL INFUSION OF PYRUVATE ON PANCREATIC HORMONE RESPONSE DURING EXERCISE

The purpose of the present investigation was to evaluate the effects o f a small infusion of pyruvate into the hepatic portal vein on the pan creatic hormone response during exercise (30-min treadmill run; 26 m/m in, 0% grade) in adrenodemedullated rats. Resting and exercising rats were infused with either pyruvate (5% solution; 0.016 ml/min) into the portal vein, pyruvate into the jugular vein, or saline into the porta l vein. Peripheral and portal blood glucose concentrations were decrea sed (P < 0.01) similarly in all groups after the exercise period. Peri pheral insulin, glucagon, and norepinephrine levels, either at rest or after exercise, were not significantly affected by the infusions. The response of portal pancreatic hormone concentrations to exercise was, however, reduced by the pyruvate infused into the portal and jugular veins for insulin and into the portal vein only for glucagon. The norm al increase in peripheral glucagon-insulin molar ratio during exercise was shut down by the infusion of pyruvate into the portal vein but no t by the infusion of pyruvate into the jugular vein or by the infusion of saline. These results indicate that a small blood infusion of pyru vate, even in the presence of a decreasing blood glucose level, can at tenuate substantially the pancreatic hormone response during exercise in adrenodemedullated rats.