개의 작은창자에서 본 포도당의 흡수 기전

Abstract

One intestinal loop of 20 em in length was made by ligating both ends of the loop of jejenum in 15 mongrel dogs. The canule was placed into mesenteric vein draining the intestinal loop. 20 cc of saline containing 200 mg% glucose was incubated for 20 minutes in each intestinal loop. Concentration gradient was made across the bloodlumen barrier by injecting 50% glucose into the jugular vein. According to the magnitude of glucose concentration gradient, experiment was grouped into three. Concentration gradient across blood-lumen barrier averaged-l-LlLz mgs; in the first group.+16.4 mg% in the second group and +60.2 mg% in the third group. The results were as follows: 1) True glucose absorption rate, represented by disappearance rate of glucose from the incubation medium, increased with the increment of concentration gradients, i.e., the rate was 93.6±3. 3 mg/ hr /loop in the first group. 71.7±2.0 mg/hr/loop in the second, and 62.9±4.9 mg/hr/loop in the third group. Apparent glucose absorption rates. represented by appearance rate of glucose in the venous blood, were relatively constant in each group. i.e., the rate was 34.2±1.6 mg/hr/loop in the first group, 35.4±1.8 mg/ - 37 hr/Ioop in the second group, and 33.2±1.8 mg/hr/loop in the third group. Hence the apparant glucose absorption rates constituted less than 50% of true glucose absorption rates. 2) Lactate appearance rates were 35.9±2.6 mg/hr/l oop in the first group. 25.1±4.0 mg/hr/Ioop in the second group, and 14.9±0.62 mg/hr/Ioop in the third group. Lactate appearance rates increased with increment of concentration gradients as in the case of true glucose absorbtion rates. Appearance rates of pyruvic acid was negligible as compared with that of lactac acid. 3) Oxygen consumption rates were 30.3±2.86 cc/hr,' oop in the first group, 30.2±1.65 cc/hr/Ioop in the second group, and 26.9± 1.43 cc/hr/Iooo. These rates were relatively constant in each group regardless of change in concentration gradients. 4) 76.4% of true glucose abrorption rates was recovered from the venous blood in the forms of glucose. lactate, and pyruvate in the first group, 77.7% in the second group, and 86.4% in the third group. These data suggest that, in dog intestine, glucose absorption is carried out partly by active mechanism and partly by diffusion. Glucose transported through active mechanism appears to be absorbed in the form of glucose molecules, whereas glucose transported through diffusion seems to be absorbed in the degraded form of lactate or pyruvate.