Oxidation of fructose by liver of the domestic fowl.

Abstract

ALTHOUGH the metabolism of carbohydrates by mammalian liver has been extensively studied, relatively little information exists regarding their metabolism by avian liver. It has been found that slices of liver from the domestic fowl (in these experiments a strain of White Leghorn) when incubated at 41.3° in a saline buffered with phosphate oxidize fructose, the rate of oxygen uptake being linear for at least 3 hr. and considerably in excess of that of control slices incubated in the absence of fructose. This was found with both male and female birds up to 1 year of age (the oldest examined) and did not depend on the bird being in lay, non-laying or in moult, or whether it was fasted or fed. Of other substrates tested in addition to fructose, sorbose, pyruvate, succinate and glutamate supported an increased oxygen uptake. Glucose, galactose, man-nose, D-tagatose, mannitol, dulcitol, sorbitol, ribose, glycerol, β-glycerophosphate, 2- and 3-phosphoglycerate, citrate, malate and β-hydroxybutyrate did not increase the uptake of oxygen above that of control slices in the absence of added substrate. The increased oxygen uptake in the presence of fructose was also obtained at 37.5°. In contrast, the oxygen uptake of slices of rat liver was not enhanced by fructose at either temperature. The uptake of fructose by slices of avian liver was not affected by concentrations of glucose up to twelve times that of fructose and was only slightly suppressed by concentrations of glucosamine which suppressed glucose uptake by 80–85 per cent.