Meeting Abstract
Phenotypic plasticity potentially affects all aspects of an organism’s adult phenotype. As an example, many studies have demonstrated (adaptive) training effects in response to exercise. In lab rats and mice, 8 weeks of forced or voluntary exercise generally causes many such changes. However, for many traits the amount of training is quantitatively related to the amount of exercise and/or depends on genetic background (e.g., not all individuals train). In the present study, we examined training effects in response to voluntary wheel running over a 4-week period in adult female mice from 4 replicate, selectively bred High Runner (HR) and 4 non-selected control (C) lines. HR mice ran ~3-fold more revolutions/day than C over the course of the study. Wheel access significantly (P<0.05) reduced total fat mass and HR mice had less fat than C, based on MRI, with no interaction; however, neither factor affected lean mass. With body mass as a covariate, wheel access also reduced both reproductive and subdermal fat pad masses, the latter especially in C mice. With body mass as covariate, wheel access increased heart mass and HR mice had larger hearts, with no interaction; HR mice also had larger brains. Hematocrit and the relative masses of triceps surae muscles, liver, and spleens were unaffected by either wheel access or linetype. Overall, results show that voluntary exercise for as little as 4 weeks can alter morphological phenotypes of adult female mice, even those that do not engage in high levels of exercise.
