Alsop Derek, Ng Tania Y-T, Chowdhury M Jasim, Wood Chris M
Department of Biology, McMaster University, 1280 Main Street West, Hamilton ON L8S 4K1, Canada.
International Lead Association (ILA), 2530 Meridian Parkway, Suite 115, Durham, NC 27713, USA.
Aquat Toxicol. 2016 Aug;177:343-54. doi: 10.1016/j.aquatox.2016.06.007. Epub 2016 Jun 16.
In Pb-contaminated environments, simultaneous exposure to both waterborne and dietborne Pb is likely to occur. This study examined the potential interactive effects of these two pathways in juvenile rainbow trout that were exposed to Pb in the water alone, in the diet alone, and in combination for 7 weeks. The highest waterborne Pb concentration tested (110μgL(-1)) was approximately equivalent to the 7-week LC20 (97μgL(-1)) measured in a separate trial, while the lowest was a concentration often measured in contaminated environments (8.5μgL(-1)). The live diet (10% daily ration on a wet mass basis) consisted of oligochaete worms (Lumbriculus variegatus) pre-exposed for 28days to the same waterborne Pb concentration, and the highest dietary dosing rate to the trout was 12.6μg Pb g fish(-1)day(-1). With waterborne exposure, whole body Pb burden increased to a greater extent in the worms than in the fish. Nonetheless, in trout waterborne exposure still resulted in 20-60-fold greater Pb accumulation compared to dietborne Pb exposure. However, combined exposure to both waterborne and dietborne Pb reduced the whole body accumulation extensively at waterborne Pb>50μgL(-1), with similar antagonistic interaction in liver and carcass (but not gill or gut) at a lower threshold of 20μgL(-1). Growth effects in trout were minimal with marginal reductions in the dietborne and combined exposures seen only at 110μgL(-1). Chronic Pb exposure reduced lipid and carbohydrates level in the worms by 50% and 80% respectively, while protein was unchanged, so growth effects in trout may have been of indirect origin. After 7 weeks, Ca(2+) homeostasis in the trout was unaffected, but there were impacts on Na(+). Blood Na(+) was reduced in waterborne and dietborne exposures, while gut Na(+)/K(+) ATPase activities were reduced in waterborne and combined exposures. This study is the first, to our knowledge to examine the interaction of waterborne and dietborne Pb exposure in fish. While physiological impacts of Pb were observed in both worms and fish, higher concentrations of dietborne Pb actually protected fish from waterborne Pb bioaccumulation and these effects. The impacts of metals on diet quality should not be neglected in future dietborne toxicity studies using live prey.
在铅污染的环境中，水生和饮食源铅的同时暴露很可能会发生。本研究调查了这两种暴露途径对虹鳟幼鱼的潜在交互作用，这些幼鱼分别单独暴露于水中的铅、饮食中的铅以及两者组合的环境中达7周之久。所测试的最高水生铅浓度（110μg/L）大约相当于在另一项试验中测得的7周半数致死浓度（LC20，97μg/L），而最低浓度则是在污染环境中经常测得的浓度（8.5μg/L）。活饵（按湿重计算每日投喂量为10%）由预先在相同水生铅浓度下暴露28天的寡毛类蠕虫（颤蚓）组成，鳟鱼的最高饮食给药率为12.6μg铅/克鱼体重/天。通过水生暴露，蠕虫体内全身铅负荷的增加幅度大于鱼类。尽管如此，与饮食源铅暴露相比，在鳟鱼中水生暴露导致的铅积累量仍高出20至60倍。然而，当水生铅浓度>50μg/L时，水生和饮食源铅的联合暴露会大幅降低全身铅积累量，在较低阈值20μg/L时，肝脏和鱼体（但鳃或肠道未出现）中也存在类似的拮抗作用。鳟鱼的生长效应微乎其微，仅在110μg/L时，饮食源和联合暴露组出现了轻微的生长减少。长期铅暴露分别使蠕虫体内的脂质和碳水化合物水平降低了50%和80%，而蛋白质水平未变，因此鳟鱼的生长效应可能是间接产生的。7周后，鳟鱼体内的Ca(2+) 稳态未受影响，但对Na(+) 有影响。水生和饮食源暴露组的血液Na(+) 降低，而水生和联合暴露组的肠道Na(+)/K(+) ATP酶活性降低。据我们所知，本研究首次考察了鱼类中水生和饮食源铅暴露的相互作用。虽然在蠕虫和鱼类中均观察到了铅的生理影响，但较高浓度的饮食源铅实际上保护了鱼类免受水生铅生物积累及这些影响。在未来使用活饵进行的饮食源毒性研究中，不应忽视金属对饵料质量的影响。
