Does reproduction protect against oxidative stress?

A central principle of life-history theory is that parents trade investment in reproduction against that in body maintenance. One physiological cost thought to be important as a modulator of such trade-off is oxidative stress. Experimental support for this hypothesis has, however, proved to be contradictory. In this study, we manipulated the nestling rearing effort of captive canaries (Serinus canaria) soon after the hatching of their nestlings using a brood-size manipulation to test whether an increase in nestling rearing effort translates into an increase in oxidative damage, an increase in ceruloplasmin (which is upregulated in response to oxidative damage) and a decrease in thiol antioxidants. We also compared the blood oxidative stress level of reproducing birds with that of non-reproducing birds, a crucial aspect that most studies have invariably failed to include in tests of the oxidative cost of reproduction. Compared with non-breeding canaries and pre-manipulation values, plasma oxidative damage (reactive oxygen metabolites and protein carbonyls) decreased in breeding canaries irrespective of sex and brood size. In contrast, oxidative damage did not change in non-breeding birds over the experiment. Ceruloplasmin activity in plasma and both non-protein and protein thiols in red blood cells did not change throughout the experiment in both treatment groups. Our results suggest that reproduction may result in decreased rather than increased blood oxidative stress. Our results may explain some of the inconsistencies that have so far been reported in experimental tests of the oxidative cost of reproduction hypothesis.

Costantini D ，Casasole G ，Eens M 《-》

Nestling rearing is antioxidant demanding in female barn swallows (Hirundo rustica).

Costantini D ，Bonisoli-Alquati A ，Rubolini D ，Caprioli M ，Ambrosini R ，Romano M ，Saino N ... -  《-》

Physiological adaptations to reproduction. I. Experimentally increasing litter size enhances aspects of antioxidant defence but does not cause oxidative damage in mice.

Garratt M ，Pichaud N ，King ED ，Brooks RC ... -  《-》

Reproduction is not costly in terms of oxidative stress.

One of the core assumptions of life-history theory is the negative trade-off between current and future reproduction. Investment in current reproduction is expected to decrease future reproductive success or survival, but the physiological mechanisms underlying these costs are still obscure. To test for a role of oxidative stress, we measured oxidative damage to lipids and proteins in liver, heart, kidneys and muscles, as well as the level of antioxidants (total glutathione and catalase), in breeding and non-breeding bank voles. We used females from lines selected for high aerobic metabolism and non-selected control lines and manipulated their reproductive investment by decreasing or increasing litter size. Unlike in most previous studies, the females reared four consecutive litters (the maximum possible during a breeding season). Contrary to predictions, oxidative damage in reproducing females was decreased or not changed, and did not differ between the selected and control lines. Oxidative damage to lipids and proteins in the liver was lower in females that weaned enlarged litters than in non-breeding ones, and was intermediate in those with reduced litters. Oxidative damage to proteins in the heart also tended to be lower in breeding females than in non-breeding ones. A negative relationship between the level of oxidative damage and activity of catalase in kidneys indicated a protective action of antioxidants. In conclusion, our study falsified the hypothesis that oxidative stress is a part of the proximate physiological mechanism underlying the fundamental life-history trade-off between current and future reproduction.

Ołdakowski Ł ，Wasiluk A ，Sadowska ET ，Koteja P ，Taylor JR ... -  《-》

An experimental manipulation of life-history trajectories and resistance to oxidative stress.

Alonso-Alvarez C ，Bertrand S ，Devevey G ，Prost J ，Faivre B ，Chastel O ，Sorci G ... -  《EVOLUTION》