SELECTION FOR GROWTH DOES NOT AFFECT APPARENT ENERGETIC EFFICIENCY OFJEJUNAL GLUCOSE-UPTAKE IN MICE

Five-wk-old male mice from high growth (M16) and randomly bred control (ICR) lines, plus their reciprocal crosses, ICR x M16 and M16 x ICR, were used to investigate whether whole-body O-2 consumption, jejunal r espiration,jejunal glucose absorption and the apparent energetic effic iency of jejunal active glucose uptake in mice are altered by genetic selection for growth as well as by heterosis and maternal effects. Who le-body O-2 consumption was measured in 12 mice from each line or cros s. The mice were later killed for measurement of jejunal O-2, using ti ssue respiration chambers and jejunal glucose transport determined by H-3-3-0-methylglucose accumulation. No heterosis or maternal effects w ere detected in jejunal glucose active transport and active glucose up take. Selection for growth (M16 vs. ICR) increased daily gain (1.54 vs . 1.09 g, P < 0.001), small intestinal length and weight, but did not enhance jejunal glucose transport. The apparent energetic efficiency o f jejunal active glucose uptake among lines was not different (54.0, 5 0.4, 51.6 and 47.1 nmol ATP expended/nmol glucose uptake for M16, ICR, M16 x ICR and ICR x M16, respectively, P > 0.63). Selection for growt h in mice did not result in more energetically efficient jejunal gluco se absorption.