Fisheries and Oceans Canada, Institute of Ocean Sciences, 9860 West Saanich Rd, P.O. Box 6000, Sidney, BC, Canada V8L 4B2.
Aquat Toxicol. 2012 Mar;109:185-93. doi: 10.1016/j.aquatox.2011.09.021. Epub 2011 Oct 6.
Increasing emissions of anthropogenic mercury represents a growing concern to the health of high trophic level marine mammals. In its organic form, this metal bioaccumulates, and can be toxic to several physiological endpoints, including the immune system. In this study, we (1) evaluated the effects of inorganic mercury (mercuric chloride, HgCl2) and organic mercury (methylmercuric chloride, MeHgCl) on the in vitro function of lymphocytes isolated from the peripheral blood of beluga whales (Delphinapterus leucas); (2) characterized the potential protective effects of sodium selenite (Na2SeO3) on cell proliferation of HgCl2 or MeHgCl-treated beluga whale lymphocytes; and (3) compared these dose-dependent effects to measurements of blood Hg in samples collected from traditionally harvested beluga whales in the western Canadian Arctic. Lymphocyte proliferative responses were reduced following exposure to 1 μM of HgCl2 and 0.33 μM of MeHgCl. Decreased intracellular thiol levels were observed at 10 μM of HgCl2 and 0.33 μM of MeHgCl. Metallothionein induction was noted at 0.33 μM of MeHgCl. Concurrent exposure of Se provided a degree of protection against the highest concentrations of inorganic Hg (3.33 and 10 μM) or organic Hg (10 μM) for T-lymphocytes. This in vitro protection of Se against Hg toxicity to lymphocytes may contribute to the in vivo protection in beluga whales exposed to high Hg concentrations. Current Hg levels in free-ranging beluga whales from the Arctic fall into the range of exposures which elicited effects on lymphocytes in our study, highlighting the potential for effects on host resistance to disease. The implications of a changing Arctic climate on Hg fate in beluga food webs and the consequences for the health of beluga whales remain pressing research needs.
人为汞排放的增加对处于食物链较高营养级别的海洋哺乳动物的健康构成了越来越大的威胁。这种金属以有机形式存在时会生物累积，并且对包括免疫系统在内的多个生理终点具有毒性。在本研究中，我们：(1) 评估了无机汞（氯化汞，HgCl2）和有机汞（甲基汞氯化物，MeHgCl）对来自白鲸（Delphinapterus leucas）外周血的淋巴细胞体外功能的影响；(2) 表征了亚硒酸钠（Na2SeO3）对 HgCl2 或 MeHgCl 处理的白鲸淋巴细胞增殖的潜在保护作用；(3) 将这些剂量依赖性效应与从加拿大西部北极地区传统收获的白鲸样本中采集的血液 Hg 测量值进行了比较。暴露于 1 μM 的 HgCl2 和 0.33 μM 的 MeHgCl 后，淋巴细胞的增殖反应受到抑制。在 10 μM 的 HgCl2 和 0.33 μM 的 MeHgCl 下观察到细胞内巯基水平降低。在 0.33 μM 的 MeHgCl 下观察到金属硫蛋白的诱导。在最高浓度的无机汞（3.33 和 10 μM）或有机汞（10 μM）存在下，硒的同时暴露为 T 淋巴细胞提供了一定程度的保护。Se 对淋巴细胞中 Hg 毒性的这种体外保护作用可能有助于在暴露于高 Hg 浓度的白鲸中提供体内保护。来自北极的自由放养白鲸的当前 Hg 水平落入了我们研究中引起淋巴细胞效应的范围，突出了对宿主对疾病的抵抗力产生影响的潜力。北极地区气候变化对 beluga 食物网中 Hg 命运的影响以及对 beluga 健康的后果仍然是紧迫的研究需求。
