SEMER, A.; PROSTROLLO*, A.*; WATERS, R.P.; KOCH, L.G.; BRITTON, S.L.; RENNER, K.J.; SWALLOW, J.G.; Univ. of South Dakota; Univ. of South Dakota; Univ. of South Dakota; Medical College of Ohio; Medical College of Ohio; Univ. of South Dakota; Univ. of South Dakota; : FOOD CONSUMPTION AND BODY COMPOSITION OF RATS SELECTED FOR ENDURANCE RUNNING CAPACITY
Swallow and colleagues previously showed that voluntary activity and body size (Swallow et al. 1999) are genetically correlated in house mice. To test the generality of this finding, we investigated the effects of genetic selection and prolonged wheel access (8 weeks) on food consumption and body composition in lines of rats selected for high and low treadmill endurance capacity (Koch and Britton, 2001). Rats from high lines ran significantly more rev/day on activity wheels than rats from control or low lines, lending support to the hypothesis that voluntary activity and physiological capacity are genetically correlated. Both treatments (selection and wheel access) significantly influenced food consumption; access to running wheels and selection for high endurance capacity resulted in increased food consumption. A significant GxE interaction was also apparent; rats in the high line with access to running wheels consumed the most food. At the end of the study, body mass differed significantly between the selected lines with the high lines weighing the least and the low lines weighing the most. Access to running wheels did not result in differences in body mass, although rats from the wheel access group were significantly leaner. Selection for high endurance capacity resulted in hypertrophy of the heart, kidney, and stomach. Interestingly, we found significant phenotypic plasticity in organ mass as a result of wheel access. Access to running wheels resulted in hypertrophy of the heart, liver, stomach, small intestine, and large intestine. The hypertrophy of the gastrointestinal tract may function to accommodate the increased food intake and nutrient demand of voluntary activity.
