The Concentrations of Fructose, Glucose and Lactate in the Splanchnic Blood Vessels of Rats Absorbing Fructose

Abstract

The concentrations of fructose, glucose and lactate were measured in the hepatic portal vein, hepatic vein and systemic aorta of fed and fasting rats given a large meal of fructose by gastric intubation. The maximum concentration of fructose found in portal vein blood was within the range 20–40 mg/100 ml. The corresponding range in the systemic circulation was 2–6 mg/100 ml. A fractional hepatic fructose uptake of 54.9% and 71.5% was found in fed and fasting rats, respectively. Little fructose was removed by extrahepatic tissues. Fructose feeding lowered the concentration of glucose in the hepatic vein of fed animals but did not alter glucose concentrations in any other vessels sampled in fed or fasting rats. The absorption of fructose raised blood lactate concentrations in all vessels sampled of both fed and fasting animals. It is suggested that this effect is due to reduction in hepatic uptake of lactate. Fructose feeding did not increase lactate production by the intestine, neither was there any evidence of significant intestinal conversion of fructose to glucose.