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Steady-state metabolism and transport of D-glucose by rat small intestine in vitro.

ABSTRACT: 1. Conditions of incubation of everted sacs of rat small intestine were selected to ensure that absorption of d-glucose by mucosal tissue from the incubation medium, intracellular metabolism of the absorbed glucose and transport of glucose through the intact intestinal tissue proceeded linearly with respect to time of incubation within stated time intervals. 2. Under these experimental conditions, steady intracellular concentrations of glucose and lactate were demonstrated. 3. The quantitative translocational and metabolic fate of absorbed glucose was determined under these steady-state conditions. About 25% of glucose absorbed from the external mucosal solution was accumulated (temporarily) within mucosal tissue and about 25% transported through the intact tissue into the external serosal solution; the remainder (about 50%) of the absorbed glucose was metabolized, 90% to lactate and 10% to CO(2). Concomitant respiration rates were comparable with those reported for several other preparations of intestine and were stoicheiometrically in excess of the O(2) metabolism required to account for the production of CO(2) from the absorbed glucose. 4. Water transport through the everted sacs proceeded at an optimum rate under the experimental conditions selected. 5. Some other observations are recorded which influenced the design of the experiments and the interpretation of results; these include the initial physiological state of the animal, the anaesthetic used and the ionic composition of the incubation medium.

SUBMITTER: Pritchard PJ

PROVIDER: S-EPMC1164752 | biostudies-other | 1977 Apr

REPOSITORIES: biostudies-other

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Project description:1. The effect of perfusion on the activities of hexokinase and lactate dehydrogenase was studied in the proximal half of the small intestine of fed and starved rats. 2. Perfusion of preparations from starved rats with a medium containing glucose caused a significant increase in hexokinase activity of the particle-free supernatant. The increase in activity was observed as early as 5min after the start of perfusion and persisted for up to 66min of perfusion. No increase in hexokinase activity of the particle-free supernatant was observed when a medium containing mannitol was used. As a further control, preparations from fed rats were perfused under the same conditions. With the medium containing glucose, the hexokinase activity of the particle-free supernatant remained unchanged during the first 15min of perfusion and thereafter fell gradually until, after 66min of perfusion, 73% of the original activity was retained. 3. The activity of lactate dehydrogenase in the particle-free supernatant prepared from the proximal half of the untreated small intestine of starved rats was significantly lower than in corresponding preparations from fed animals. However, it did not change significantly on perfusion with media containing either mannitol or glucose. 4. The distribution of hexokinase activity between total particulate fraction and particle-free supernatant was measured in preparations from starved rats after perfusion for 5-10min. In preparations that had not been perfused the ratio of hexokinase activity in total particulate fraction/particle-free supernatant was significantly higher in starved than in fed animals. After perfusion with a medium containing glucose, the total homogenate activity had not changed significantly, whereas the ratio of hexokinase activity in total particulate fraction/particle-free supernatant decreased significantly and approached the value obtained with fed animals. 5. The results agree with the view that the glucose-dependent increase of hexokinase activity in the soluble cell compartment as observed in vivo and in vitro in the intestinal mucosa of starved rats is brought about by a release of hexokinase activity from a particulate subcellular structure(s).

Project description:To investigate the effects of the somatostatin analogue, octreotide, on maltose and sucrase activities and expression of glucose transporter type 2 (GLUT2) in obese rat intestinal mucosa.We divided 49 Sprague-Dawley rats into a group of 31 high fat diet-induced obese rats and a group of 18 normal controls. The obese rats were separated into an octreotide treated group of 16 rats and an obese group of 15. The intervention group was injected with octreotide at 40 ?g/kg body weight every 12 h for 8 d. Rat body weight was measured weekly to calculate Lee's index. After euthanization, maltase and sucrase activities in the small intestine were measured by activity assays, and the fasting plasma glucose level was measured. The expression of GLUT2 in small intestinal mucosa was analyzed by immunohistochemistry, reverse transcriptase polymerase chain reaction and Western blotting assays.Body weight, Lee's index, fasting plasma glucose level, maltase activity in small intestinal mucosa, mucosa and apical GLUT2, GLUT2 mRNA and protein expression levels were all significantly higher in the obese group than in the normal control group (605.61 ± 141.00 vs 378.54 ± 111.75, 337.61 ± 10.82 vs 318.73 ± 20.10, 8.60 ± 1.38 vs 7.33 ± 0.70, 156.01 ± 58.81 vs 50.43 ± 30.49, 390 744.2 ± 62 469.21 vs 170 546.50 ± 50 646.14, 26 740.18 ± 3809.60 vs 354.98 ± 57.19, 0.26 ± 0.11 vs 0.07 ± 0.02, and 2.08 ± 0.59 vs 1.27 ± 0.38, respectively, all P < 0.01). Sucrase activity did not differ between the two groups. Octreotide intervention significantly decreased the body weight and fasting plasma glucose level of obese rats (508.27 ± 94.39 vs 605.61 ± 141.00, 7.58 ± 1.51 vs 8.60 ±1.38, respectively, all P < 0.05). The intestinal mucosa and apical GLUT2, expression of GLUT2 mRNA and protein were also significantly lower in the octreotide intervention group than in the obese group (269 975.2 ± 53 730.94 vs 390 744.2 ± 62 469.21, 3758.06 ±364.51 vs 26 740.18 ± 3809.60, 0.08 ± 0.02 vs 0.26 ±0.11, and 1.31 ± 0.27 vs 2.08 ± 0.59, respectively, all P < 0.01).High fat diet-induced obesity is associated with elevated intestinal maltase activity, GLUT2 expression, and permanent apical GLUT2 in the small intestinal mucosa of rats. Octreotide can inhibit these effects.

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Steady-state metabolism and transport of D-glucose by rat small intestine in vitro.

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