Meeting Abstract

52.3  Jan. 6  Effects of Voluntary Activity and Genetic Selection on Muscle Metabolic Capacities and Organ Masses in House Mice KELLY, SA*; GOMES, FR; KOLB, EM; MALISCH, JL; GARLAND, T, JR.; Univ. of California, Riverside skell005@student.ucr.edu

Studies of rodents have generally found that chronic voluntary exercise causes elevations in total daily energy expenditure (DEE) that also entail increases in food consumption, which may result in compensation by internal organs that support nutrient extraction and utilization. In addition, species that naturally have higher DEE often have larger relevant processing organs, which could represent innate differences and/or phenotypic plasticity. We tested for changes in organ masses of 4 replicate lines of house mice that had been selectively bred for high voluntary wheel running (S lines) for 37 generations as compared with 4 non-selected control (C) lines. Females were housed either with or without wheel access for 13-14 weeks beginning at 53-60 days of age. We also measured hematocrit, citrate synthase activity, and myoglobin concentration. As in previous studies, both selection for high activity and chronic wheel access reduced body mass, with additive effects (no statistical interaction). Body mass was a significant predictor of all traits except citrate synthase and myoglobin, so all results reported are from ANCOVAs. Several traits were significantly affected by selection history and/or wheel access, but interactions between these two main effects were never significant (all P > 0.05). With body mass as a covariate, mice from S lines had significantly larger ventricles, with more myoglobin. Wheel access increased ventricle and kidney size, and skeletal muscle citrate synthase activity and myoglobin concentration. S-line individuals with the mini-muscle phenotype (homozygous for a Mendelian recessive allele that halves hindlimb muscle mass) had larger ventricles, spleens, livers, kidneys, lungs, and stomachs. Surprisingly, stomach, intestine, and caecum masses were not significantly affected by any factor. Supported by NSF IOB-0543429 to T.G.