Adeyemo Olanike K
University of Ibadan, Fish and Wildlife Unit, Department of Veterinary Public Health and Preventive Medicine, Ibadan, Nigeria.
J Environ Health. 2008 May;70(9):48-51.
Sublethal levels of pollutants usually cause biochemical or physiological effects at the subcellular level in an organism. Death is too extreme a criterion for determination of whether a substance is harmful or not; it is therefore important to find biomarkers of health and sublethal toxicant effects. In the 11 local-government areas of Ibadan, a large metropolitan area in Nigeria, previous studies of lead levels in surface water and fish ponds revealed surface water levels in ranges of 0.5-2.35 mg/L (mean = 0.76 mg/L) during the dry season and 1.15-2.20 mg/L (mean = 1.34 mg/L) during the rainy season, and a range of 1.09-2.9 mg/L (mean = 1.88 mg/L) in fish ponds. In the study reported here, Clarias gariepinus was exposed to environmentally relevant concentrations (0.0, 0.05, 0.1, 0.5, and 1 mg/L) of lead nitrate over a period of eight weeks. The goal was to assess histological alterations in the gills and ovaries. The lesions observed in the gills included epithelial hyperplasia, atrophy and fusion of gill filaments, and marked degeneration and necrosis of the epithelial cells, with hemorrhages and marked disorganization and rupture in the secondary lamellae. In the ovaries, diffuse mild degeneration and necrosis of the follicles were initially observed; subsequently, the groups exposed to higher concentrations of lead nitrate showed marked severe degeneration of ovarian follicles. The results of this work clearly indicate that lead has adverse effects on the gills and ovaries of Clarias gariepinis. The severity of lesions caused by lead nitrate was positively correlated with the concentration.
污染物的亚致死水平通常会在生物体的亚细胞水平上引起生化或生理效应。死亡作为判断一种物质是否有害的标准过于极端；因此，找到健康和亚致死毒性效应的生物标志物非常重要。在尼日利亚一个大都市伊巴丹的11个地方政府区域，之前对地表水和鱼塘中铅含量的研究表明，旱季地表水铅含量范围为0.5 - 2.35毫克/升（平均 = 0.76毫克/升），雨季为1.15 - 2.20毫克/升（平均 = 1.34毫克/升），鱼塘中铅含量范围为1.09 - 2.9毫克/升（平均 = 1.88毫克/升）。在本报告的研究中，将非洲鲶鱼暴露于环境相关浓度（0.0、0.05、0.1、0.5和1毫克/升）的硝酸铅中，持续八周时间。目的是评估鳃和卵巢的组织学变化。在鳃中观察到的病变包括上皮增生、鳃丝萎缩和融合，以及上皮细胞的明显退化和坏死，伴有出血以及次生鳃小片明显的紊乱和破裂。在卵巢中，最初观察到卵泡弥漫性轻度退化和坏死；随后，暴露于较高浓度硝酸铅的组显示卵巢卵泡明显严重退化。这项工作的结果清楚地表明，铅对非洲鲶鱼的鳃和卵巢有不良影响。硝酸铅引起的病变严重程度与浓度呈正相关。
