|
| |
|
|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
First published online December 14, 2005
Journal of Experimental Biology 209, 115-127 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.01883
Maximum aerobic performance in lines of Mus selected for high wheel-running activity: effects of selection, oxygen availability and the mini-muscle phenotype
Department of Biology, University of California, Riverside, CA 92521, USA
* Author for correspondence at present address: Integrative Ecology Group, Estación Biológica de Doñana, CSIC, Apdo. 1056, E-41080 Seville, Spain (e-mail: enrico.rezende{at}ebd.csic.es)
Accepted 10 September 2005
We compared maximum aerobic capacity during forced exercise
(
O2max) in
hypoxia (PO2=14% O2), normoxia (21%) and
hyperoxia (30%) of lines of house mice selectively bred for high voluntary
wheel running (S lines) with their four unselected control (C) lines. We also
tested for pleiotropic effects of the `mighty mini-muscle' allele, a Mendelian
recessive that causes a 50% reduction in hind limb muscle but a doubling of
mass-specific aerobic enzyme activity, among other pleiotropic effects.
O2max of female
mice was measured during forced exercise on a motorized treadmill enclosed in
a metabolic chamber that allowed altered PO2. Individual
variation in
O2max was highly
repeatable within each PO2, and values were also
significantly correlated across PO2. Analysis of
covariance showed that S mice had higher body-mass-adjusted
O2max than C at
all PO2, ranging from +10.7% in hypoxia to +20.8% in
hyperoxia. O2max
of S lines increased practically linearly with PO2,
whereas that of C lines plateaued from normoxia to hyperoxia, and respiratory
exchange ratio (=CO2
production/O2max)
was lower for S lines. These results suggest that the physiological
underpinnings of
O2max differ
between the S and C lines. Apparently, at least in S lines, peripheral tissues
may sustain higher rates of oxidative metabolism if central organs provide
more O2. Although the existence of central limitations in S lines
cannot be excluded based solely on the present data, we have previously
reported that both S and C lines can attain considerably higher
O2max during
cold exposure in a He-O2 atmosphere, suggesting that limitations on
O2max depend on
interactions between the central and peripheral organs involved. In addition,
mini-muscle individuals had higher
O2max than did
those with normal muscles, suggesting that the former might have higher
hypoxia tolerance. This would imply that the mini-muscle phenotype could be a
good model to test how exercise performance and hypoxia tolerance could evolve
in a correlated fashion, as previous researchers have suggested.
Key words: artificial selection, central limitation, exercise, hypoxia, hyperoxia, maximum metabolic rate, oxygen availability, peripheral limitation, respiratory exchange ratio, symmorphosis
This article has been cited by other articles:
|
|
 |
|
  E. L. Rezende, F. R. Gomes, J. L. Malisch, M. A. Chappell, and T. Garland Jr. Maximal oxygen consumption in relation to subordinate traits in lines of house mice selectively bred for high voluntary wheel running J Appl Physiol, August 1, 2006; 101(2): 477 - 485. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. Garland Jr and S. A. Kelly Phenotypic plasticity and experimental evolution J. Exp. Biol., June 15, 2006; 209(12): 2344 - 2361. [Abstract] [Full Text] [PDF]
|
|
