Department of Biology, University of Louisiana at Lafayette, Lafayette, LA 70504, United States.
Aquat Toxicol. 2013 Apr 15;130-131:51-7. doi: 10.1016/j.aquatox.2013.01.001. Epub 2013 Jan 9.
We investigated the occurrence of copper acclimation in the least killifish, Heterandria formosa using both lethal and sublethal endpoints. We also investigated potential mechanisms underlying the observed acclimation. To assess the occurrence of acclimation, fish were exposed to either a background Cu level or to 15 μg/L Cu for seven days and subsequently exposed to a lethal Cu level (150 μg/L Cu). During the latter exposure, fish were monitored for survival till all fish had died, and (during the first 8h of this exposure) for changes in whole-body Na levels and lipid peroxidation (LPO). During the high-level Cu exposure, fish pre-exposed to copper had a significantly longer time-to-death than did the control fish. Similarly, neither whole-body Na nor LPO changed in the Cu-pre-exposed fish during the 8h of the exposure to 150 μg/L Cu - while both decreased significantly in the control fish. Thus, acclimation was evident for both time-to-death and the sublethal endpoints. These results also indicate that Cu toxicity may involve both Na loss and LPO, and that Cu-acclimation may be brought about by prevention of these effects. Our follow-up study on potential mechanisms underlying this copper acclimation used a similar pre-exposure/exposure design. Fish were subsampled at the end of the 7-day acclimation period - just before the commencement of high-level Cu exposure (T), after 4h of this Cu exposure (T), and again after 8h of this Cu exposure (T). Whole-body Cu accumulation, Na/K-ATPase activity, metallothionein levels, and catalase activity were quantified for these time points. While Cu levels were higher in the Cu-pre-exposed fish than in the control fish at T, net Cu accumulation was faster in the control fish than in the Cu-pre-exposed fish during the subsequent high-level Cu exposure. Consequently, changes in Cu accumulation dynamics may play a role in the resistance. Metallothionein induction may also play a role in the observed acclimation, as Cu-acclimated fish had a significantly higher metallothionein concentration compared to the control fish. There was no evidence of involvement of Na/K-ATPase in the acclimation, as the activity of this enzyme remained lower in the pre-exposed fish than in the control fish throughout both Cu exposure periods. There was limited evidence that a reduced loss of catalase activity plays a role in the acclimation; catalase activity did not differ after the pre-exposure period but was significantly higher in Cu-acclimated fish than in the control fish at T.
我们使用致死和亚致死终点研究了最微小的丽鱼 Heterandria formosa 体内铜适应的发生。我们还研究了观察到的适应现象背后的潜在机制。为了评估适应的发生，鱼被暴露于背景铜水平或 15μg/L 铜中 7 天，然后暴露于致死铜水平（150μg/L 铜）。在后者暴露期间，监测鱼的存活时间，直到所有鱼都死亡，并（在暴露于 150μg/L 铜的前 8 小时）监测鱼体内的全身 Na 水平和脂质过氧化（LPO）变化。在高铜暴露期间，与对照组鱼相比，预先暴露于铜的鱼死亡时间明显延长。同样，在暴露于 150μg/L 铜的前 8 小时内，预先暴露于铜的鱼体内的全身 Na 或 LPO 均未发生变化，而对照组鱼体内的这两种物质均显著下降。因此，无论是致死终点还是亚致死终点，都可以看出适应现象。这些结果还表明，铜毒性可能涉及 Na 损失和 LPO，而铜适应可能是通过预防这些效应来实现的。我们对这种铜适应背后的潜在机制的后续研究使用了类似的预暴露/暴露设计。在 7 天适应期结束时（即在开始高铜暴露之前）、暴露于高铜 4 小时后（T）和暴露于高铜 8 小时后（T）对鱼进行了亚采样。在这些时间点定量了鱼体内的铜积累、Na/K-ATPase 活性、金属硫蛋白水平和过氧化氢酶活性。虽然 T 时预先暴露于铜的鱼体内的铜含量高于对照组鱼，但在随后的高铜暴露期间，对照组鱼体内的净铜积累速度快于预先暴露于铜的鱼。因此，铜积累动力学的变化可能在抗性中发挥作用。金属硫蛋白的诱导也可能在观察到的适应中发挥作用，因为与对照组鱼相比，铜适应的鱼体内的金属硫蛋白浓度明显更高。没有证据表明 Na/K-ATPase 参与了适应，因为在两个铜暴露期内，该酶的活性始终低于对照组鱼。有有限的证据表明，过氧化氢酶活性的降低可能在适应中发挥作用；暴露前阶段后，过氧化氢酶活性没有差异，但在 T 时，铜适应的鱼体内的过氧化氢酶活性明显高于对照组鱼。
