Meeting Abstract
86.5 Friday, Jan. 7 Effects of oxygen availability on maximum aerobic performance in mice selected for divergent BMR or high aerobic capacity GEBCZYNSKI, A K*; KONARZEWSKI, M; University of Bialystok, Poland; University of Bialystok, Poland andgebcz@uwb.edu.pl
Maximum aerobic metabolism in mammals is constrained by one (or many) of steps of oxygen transport and utilization pathways. To elucidate those constraints we compared peak metabolic rate elicited by running (VO2run) in hypoxia (14% O2), normoxia (21% O2) and hyperoxia (30% O2) of house mice divergently selected for low and high basal metabolic rate (L-BMR and H-BMR, respectively), mice selected for maximum metabolic rate elicited by swimming (VO2swim), and unselected control lines. In all line types VO2run was lowest in hypoxia, intermediate in normoxia and highest in hyperoxia, which suggests a ‘central’ limitation of oxygen uptake or delivery instead of a limit set by cellular oxidative capacity. However, the existence of a common central limitation is in disagreement with our earlier studies showing that selection on high VO2swim, (in contrast to selection on high BMR) resulted in considerably higher oxygen consumption during cold exposure in a He–O2 atmosphere than VO2run. Likewise, between-line type differences in heart mass and blood parameters are inconsistent with the notion of central limitation. While responses of VO2 to hypoxia were similar across different selection regimens, the selection lines showed contrasting responses under hyperoxic conditions. VO2run in the H-BMR line type was highest, suggesting that selection on high BMR led to increased peripheral aerobic capacity. Overall, between line type differences in the effect of PO2 on VO2run and in components of O2 flux pathways are incompatible with the notion of symmorphosis. Our results suggest that constraints on VO2max are context-dependent and determined by interactions between the central and peripheral organs and tissues comprising steps of O2 delivery.
