Testosterone and oxidative stress: the oxidation handicap hypothesis
Testosterone and oxidative stress: the oxidation handicap hypothesis
复制标题
DOI：
10.1098/rspb.2006.3764
复制
发表时间：
2007-03-22
影响因子：
4.7
通讯作者：
Sorci, Gabriele
中科院分区：
文献类型：
--
作者：
Alonso-Alvarez, Carlos;Bertrand, Sophie;Sorci, Gabriele
第二性征（SST）通常被认为是在择偶过程中作为个体品质的诚实信号而进化而来的。 SST 的诚实性是由生产/维护成本来保证的。在男性中，许多 SST 的表达是睾酮依赖性的。免疫能力障碍假说已被提出作为确保 SST 诚实的一种可能机制，其基础是睾酮除了对性信号有影响外，还具有免疫抑制作用。免疫能力缺陷假说得到了不同的支持。然而，基于睾酮的信号传导的成本不仅限于免疫抑制，还可能涉及其他生理功能，例如抗氧化机制。在这里，我们测试了这样的假设：睾酮会抑制具有睾酮依赖性性信号的物种（斑胸草雀）对氧化应激的抵抗力。雄性斑马雀接受皮下植入物填充氟他胺（一种抗雄激素）或睾酮，或保持空（对照）。与预测一致，我们发现植入氟他胺的男性中红细胞对自由基攻击的抵抗力最高，而植入睾酮的男性中红细胞对自由基攻击的抵抗力最低。我们还发现，在经过睾酮治疗的鸟类中，细胞介导的免疫反应受到抑制，这支持了免疫能力障碍的假说。最近发现，红细胞对自由基的抵抗力与该物种的死亡率呈负相关，这表明性信号的好处可能会抵消氧化带来的成本。
Secondary sexual traits (SST) are usually thought to have evolved as honest signals of individual quality during mate choice. Honesty of SST is guaranteed by the cost of producing/maintaining them. In males, the expression of many SST is testosterone-dependent. The immunocompetence handicap hypothesis has been proposed as a possible mechanism ensuring honesty of SST on the basis that testosterone, in addition to its effect on sexual signals, also has an immunosuppressive effect. The immunocompetence handicap hypothesis has received mixed support. However, the cost of testosterone-based signalling is not limited to immunosuppression and might involve other physiological functions such as the antioxidant machinery. Here, we tested the hypothesis that testosterone depresses resistance to oxidative stress in a species with a testosterone-dependent sexual signal, the zebra finch. Male zebra finches received subcutaneous implants filled with flutamide (an anti-androgen) or testosterone, or kept empty (control). In agreement with the prediction, we found that red blood cell resistance to a free radical attack was the highest in males implanted with flutamide and the lowest in males implanted with testosterone. We also found that cell-mediated immune response was depressed in testosterone-treated birds, supporting the immunocompetence handicap hypothesis. The recent finding that red blood cell resistance to free radicals is negatively associated with mortality in this species suggests that benefits of sexual signalling might trade against the costs derived from oxidation.