Glucose absorption and metabolism by the gut of rainbow trout

1. 1. Absorption and metabolism of d-glucose in vitro by perfused intact segments and incubated slices of trout gut were studied. 2. 2. Glucose moved against an apparent concentration difference into the mucosa but not through submucosal tissue into fluid bathing the serosal gut surface. 3. 3. Mean rates of glucose absorption at 24°C by perfused mid-gut were 26 and 54 μg/mg dry wt./hr with glucose concentrations of 50 and 100 mg% in the medium, respectively. Calculated transport (mucosal absorption—three-fifths total glucose utilization) was approximately 30 per cent of absorption. 4. 4. Glucose transport rate was three to six times higher in mid-gut than in caeca and hind-gut on both a weight and surface area bases. 5. 5. Absorption and transport were greatly increased by increased media temperature, glucose concentration in the medium and feeding activity, whereas rates of glycogenolysis, glycolysis and oxygen consumption remained relatively constant under the same conditions. 6. 6. Rates of all determined catabolic processes in caeca and mid-gut were of similar magnitude. 7. 7. Mucosal membranes restrict diffusion of endogenous glucose and lactate into surrounding media more than serosal membranes do.