Influence of glipizide on hepatic and peripheral insulin exchange after glucose administration

Hepatic insulin uptake was studied in five patients with portal catheters introduced through the umbilical vein remnant for diagnostic purposes. Glipizide (1,5 mg) was given intravenously followed one hour later by 20 g glucose intravenously and blood samples were drawn simultanously from the portal vein and a hepatic vein. The areas under the curves describing portal insulin and hepatic insulin were calculated. The ratio of (portal insulin area -- hepatic insulin area) /portal insulin area after glucose injection exceeded that after glipizide injection (p < 0.05). This finding indicates a greater fractional hepatic extraction of insulin after glucose than after glipizide. Healthy subjects were given 100 g glucose perorally and blood samples were drawn simultanously from a radial artery and an antecubital vein for one hour. In all cases a net insulin uptake was observed during the whole observation period. The subjects were restudied given 1.5 mg intravenously one hour before glucose administration. This time less insulin was taken up by the forearm tissues after the glucose load and in one subject insulin in venous blood samples exceeded that in corresponding arterial blood samples. It is concluded that glipizide when given before a glucose load affects the uptake of insulin by peripheral tissues during the glucose load.