Machreki-Ajmi M, Ketata I, Ladhar-Chaabouni R, Hamza-Chaffai A
Marine Ecotoxicology, UR 09-03, University of Sfax, IPEIS, BP 805, 3018, Sfax, Tunisia.
Ecotoxicology. 2008 Jan;17(1):1-11. doi: 10.1007/s10646-007-0166-9. Epub 2007 Dec 4.
The present study was designed to detect in situ effects of cadmium on marine organisms Cerastoderma glaucum from the gulf of Gabès (Tunisia). Six sampling stations were chosen: one site, relatively far from known local source of pollution, was considered as uncontaminated site and five sites clearly exposed to anthropogenic impact. Metallothionein like protein (MTLP) and sub-cellular metal partitioning were measured in cockles (C. glaucum) gills and digestive gland. Various biomarkers were also measured, including malondialdehyde (MDA) in the digestive gland and acetylcholinesterase activity (AChE) in the remainder. The health status of the cockles was assessed by using the condition index (CI). Significant differences between sites were noted for Cd concentrations, (CI) and also for the three studied biomarkers. Significant higher biomarkers response was measured in cockles from stations located in the northern part of the gulf, which are exposed directly to industrial and urban effluents, whereas the response of most biomarkers was minimal at the reference station. Positive and significant correlations were observed between MTLP and Cd concentrations in the digestive gland and in the gills. However, it must be noted that these correlations were more significant in the digestive gland, suggesting that compared to the gills, the digestive gland of C. glaucum is more suitable for monitoring metal pollution. The subcellular distribution of Cd showed that the soluble fraction was the major compartment for Cd storage, a pattern which is due to the role of MTLP in Cd detoxication. But at the most contaminated site (EH), cadmium in the digestive gland was preferentially accumulated in the insoluble fraction (P1) suggesting that the MTLP capacity in binding metals was not sufficient to avoid the binding of Cd to the insoluble fraction. Furthermore, the MTLP concentrations in the cockles from this site are lower than expected. So in highly polluted sites, MTLP in C. glaucum should not be used as a useful biomarker for metal pollution. The lipid peroxidation as presented by malondialdehyde levels, and MT-like protein concentrations increased in cockles exposed to cadmium contamination. We can, therefore, hypothesize that Cd could induce MTLP synthesis and MDA increase. While AChE had distinct and specific pattern showing that cadmium is not the only factor of the inhibition of cholinesterase activity. There are other polluting inputs engendering this inhibition.
本研究旨在检测镉对来自突尼斯加贝斯湾的海洋生物——青蛤的原位影响。选择了六个采样站：一个距离已知当地污染源相对较远的站点被视为未受污染站点，另外五个站点明显受到人为影响。测定了青蛤鳃和消化腺中的金属硫蛋白样蛋白（MTLP）以及亚细胞金属分配情况。还测定了各种生物标志物，包括消化腺中的丙二醛（MDA）和其余部分的乙酰胆碱酯酶活性（AChE）。通过使用状况指数（CI）评估青蛤的健康状况。各站点之间在镉浓度、（CI）以及三种研究的生物标志物方面均存在显著差异。在海湾北部直接暴露于工业和城市污水的站点的青蛤中，生物标志物的响应显著更高，而在参考站点大多数生物标志物的响应最小。在消化腺和鳃中，MTLP与镉浓度之间观察到正相关且显著相关。然而，必须指出的是，这些相关性在消化腺中更为显著，这表明与鳃相比，青蛤的消化腺更适合用于监测金属污染。镉的亚细胞分布表明，可溶部分是镉储存的主要区室，这种模式归因于MTLP在镉解毒中的作用。但在污染最严重的站点（EH），消化腺中的镉优先积累在不溶部分（P1），这表明MTLP结合金属的能力不足以避免镉与不溶部分结合。此外，该站点青蛤中的MTLP浓度低于预期。因此，在污染严重的站点，青蛤中的MTLP不应用作金属污染的有效生物标志物。丙二醛水平所呈现的脂质过氧化以及MT样蛋白浓度在暴露于镉污染的青蛤中增加。因此，我们可以假设镉可诱导MTLP合成和MDA增加。而AChE呈现出独特且特定的模式，表明镉不是抑制胆碱酯酶活性的唯一因素。还有其他污染输入导致这种抑制。
