SELECTION FOR BODY-COMPOSITION DOES NOT AFFECT ENERGETIC EFFICIENCY OF JEJUNAL GLUCOSE-UPTAKE IN MICE

Five-wk-old male mice from three lines were used to examine whether th e apparent energetic efficiency of active jejunal glucose uptake in mo use jejunum is altered by genetic selection for different body composi tion. The mice lines were selected as follows: HE, high percentage of body fat with no change in body weight as a constraint; LF, low percen tage of body fat; and RS, randomly bred control. Body weight was simil ar in all lines. Total jejunal O-2 consumption and ouabain-sensitive O -2 consumption,were used to estimate the energy expenditure associated with glucose absorption and Na+/K+-ATPase activity. Tritiated 3-O-met hyl-D-glucose was used to determine glucose uptake by mouse jejunum. L ine LF, when compared with line HE, had lower body fat as indicated by epididymal fat pad weight (143 vs. 362 mg/mouse, P < 0.001). There we re no significant, differences in small intestinal weight, length and density (mg/cm) between LF and HE lines. Jejunal villus width was grea ter in line LF compared with line HE (115 vs. 92 mu m, P < 0.002). Jej unal glucose transport and O-2 consumption were not different between LF and HE lines. Ouabain-sensitive O-2 consumption was not significant ly different among the three lines. No differences were noted in the a pparent energetic efficiency of active glucose uptake among lines.