Birds sacrifice oxidative protection for reproduction.
Oxidative metabolism has reactive oxygen species (ROS) as unavoidable by-products, and the damage ROS inflicts on DNA, proteins and lipids is considered to be a major agent of senescence. Increasing reproductive effort accelerates senescence, but whether reproductive effort is increased at the expense of protection against oxidative damage has not yet been tested. We manipulated reproductive effort in zebra finches through brood size manipulation and measured the activity of two major antioxidant enzymes (superoxide dismutase (SOD) and glutathione peroxidase (GPx)) in the pectoral muscle after 19-20 days of brood rearing. Oxidative stress is reflected by the balance between oxidative protection and ROS exposure, and we therefore scaled SOD and GPx activity to daily energy expenditure (DEE) as an index of ROS production. SOD and GPx activity decreased with increasing brood size by 28% and 24%, respectively. This effect was identical in the two sexes, but arose in different ways: males did not change their DEE, but had lower absolute enzyme activity, and females increased their DEE, but did not change absolute enzyme activity. This result suggests that senescence acceleration by increased reproductive effort is at least in part mediated by oxidative stress.
Wiersma
Popko
P
Zoological Laboratory of the University of Groningen, 9750 AA Haren, The Netherlands. p.wiersma@biol.rug.nl
Selman
Colin
C
Speakman
John R
JR
Verhulst
Simon
S
D000375:Aging / Q000378:metabolism* / Q000502:physiology; D000818:Animals; D004734:Energy Metabolism / Q000502:physiology; D046369:Finches / Q000378:metabolism* / Q000502:physiology; D005979:Glutathione Peroxidase / Q000378:metabolism; D016014:Linear Models; D008098:Litter Size; D018482:Muscle, Skeletal / Q000378:metabolism; D018384:Oxidative Stress / Q000502:physiology*; D012098:Reproduction / Q000502:physiology*; D012737:Sex Factors; D013482:Superoxide Dismutase / Q000378:metabolism
D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase