Regoli Francesco, Nigro Marco, Benedetti Maura, Fattorini Daniele, Gorbi Stefania
Istituto di Biologia e Genetica, Università Politecnica delle Marche, Via Ranieri Monte d'Ago, 60100 Ancona, Italy.
Aquat Toxicol. 2005 Oct 5;75(1):43-52. doi: 10.1016/j.aquatox.2005.07.003.
The Antarctic silverfish Pleuragramma antarcticum is a key organism in the ecology of Southern Ocean. Eggs with fully developed yolk-sac embryos and newly hatched larvae have been recently observed to occur in the platelet ice accumulating below the sea-ice layer. This environment has strong pro-oxidant characteristics at the beginning of austral spring, when the rapid growth of algal ice communities, the massive release of nutrients and the photoactivation of dissolved organic carbon and nitrates, all represent important sources for oxyradical formation. Such processes are concentrated in a short period of a few weeks which overlaps with the final development of P. antarcticum in platelet ice. The aim of this work was to characterize the antioxidant system in embryos of P. antarcticum and the responsiveness toward the natural increase of pro-oxidant conditions in early spring. Considering the lack of ecotoxicological data on this species and its pivotal importance in the ecosystem of Southern Ocean, the sensitivity of its early life stages was also evaluated after laboratory exposures to environmentally relevant doses of benzo(a)pyrene, as a model chemical potentially released from anthropogenic activities. Obtained results revealed a marked temporal increase of antioxidants in embryos of P. antarcticum as adaptive counteracting responses to oxidative conditions of platelet ice. Particularly prompt responses were observed for glutathione metabolism which, however, did not prevent formation of increasing levels of lipid peroxidation products; from the analysis of total oxyradical scavenging capacity (TOSC), the overall efficiency to neutralize peroxyl radicals remained almost constant while slightly lower TOSC values were obtained toward hydroxyl radicals at the end of sampling period. Laboratory exposures to 0.5-5 microg/l BaP caused a significant accumulation of this PAH but no significant effects on the activity of cytochrome P450. Antioxidants of exposed embryos showed less marked variations than embryos in field conditions suggesting that the elevated pro-oxidant challenge, to which these organisms are naturally adapted, might be responsible for the moderate responsiveness to pro-oxidant chemicals.
南极银鱼（Pleuragramma antarcticum）是南大洋生态系统中的关键生物。最近观察到，带有发育完全的卵黄囊胚胎的卵以及刚孵化的幼体出现在海冰层下方堆积的板冰中。在南极春季开始时，这种环境具有很强的促氧化剂特性，此时藻类冰群落迅速生长、大量营养物质释放以及溶解有机碳和硝酸盐的光活化，都是氧自由基形成的重要来源。这些过程集中在短短几周内，与南极银鱼在板冰中的最终发育阶段重叠。这项工作的目的是表征南极银鱼胚胎中的抗氧化系统，以及其对早春促氧化剂条件自然增加的反应能力。考虑到缺乏关于该物种的生态毒理学数据及其在南大洋生态系统中的关键重要性，还在实验室中让其暴露于环境相关剂量的苯并[a]芘（作为人为活动可能释放的典型化学物质）后，评估了其早期生命阶段的敏感性。获得的结果表明，南极银鱼胚胎中的抗氧化剂随时间显著增加，作为对板冰氧化条件的适应性抵消反应。谷胱甘肽代谢的反应尤为迅速，然而，这并未阻止脂质过氧化产物水平的升高；从总氧自由基清除能力（TOSC）分析来看，中和过氧自由基的总体效率几乎保持不变，而在采样期结束时，对羟基自由基的TOSC值略低。实验室暴露于0.5 - 5微克/升的苯并[a]芘会导致这种多环芳烃的显著积累，但对细胞色素P450的活性没有显著影响。与处于野外条件下的胚胎相比，暴露胚胎的抗氧化剂变化不太明显，这表明这些生物自然适应的升高的促氧化剂挑战可能是其对促氧化化学物质反应适度的原因。
