镉对苯并(a)芘在蚯蚓亚细胞组分中分配积累的影响

摘要

通过外源添加不同浓度镉离子(Cd2+)来研究复合污染条件下镉(Cd)对苯并(a)芘(BaP)在蚯蚓体内不同亚细胞组分(组分C:细胞溶质组分;组分D:固体颗粒组分;组分E:细胞碎片组分)中的分配积累情况,并探究其内在机制.结果表明,BaP主要分布于蚯蚓的细胞碎片组分,其次为固体颗粒组分,在细胞溶质组分中的浓度最低.在Cd2+添加处理下,随着Cd2+浓度的增加,3个细胞组分中的BaP浓度呈先降低后升高的趋势.随着Cd2+浓度的增加,3个亚细胞组分中的蛋白含量与乙酰胆碱酯酶(AChE)活性均呈先升高后下降的趋势;而蚯蚓细胞溶质和细胞碎片组分中的谷胱甘肽S-转移酶(GST)活性呈先下降后上升的趋势,但固体颗粒组分中逐渐增加.相关性分析表明,蚯蚓细胞溶质和细胞碎片组分中的蛋白含量与其对应组分中的BaP浓度呈显著负相关;细胞溶质组分中的AChE活性与该组分中的BaP浓度呈显著负相关;而GST的活性与BaP浓度没有显著相关性.综上所述,BaP主要分配积累在细胞碎片组分中,Cd2+可能通过影响蛋白含量及AChE的活性,从而影响BaP在细胞碎片和细胞溶质组分中的积累,使得BaP的浓度随着Cd2+浓度的增加呈现先降低后升高的趋势.%This experiment explored the mechanism underlying benzo[a] pyrene (BaP) distribution in different subcellular fractions of the earthworm Eisenia fetida (Fraction C:associated with the cytosol;Fractions D:associated with granules;and Fraction E:associated with tissue fragments and cell membranes) under conditions of contamination with both BaP and cadmium ions (Cd2+) at different concentrations.The results showed that Cd2+ inhibited the accumulation of BaP in the earthworm,and that BaP was accumulated to the greatest extent in Fraction E,followed by Fraction C and Fraction D.With the addition of Cd2+,BaP concentrations in the three fractions initially decreased,but subsequently increased with the increasing concentration of Cd2+,whereas protein content and acetylcholinesterase (AChE) activity showed the opposite trend.In contrast,glutathione s-transferase (GST) activity initially decreased and then subsequently increased with increasing Cd2+ concentration in Fraction C and E,whereas the activity gradually increased in Fraction D.Correlation analysis indicated that protein content showed a significant negative correlation with BaP concentration in Fraction C and E;AChE activity showed a significant negative correlation with BaP concentration in Fraction C;and GST activity showed a non-significant correlation with BaP concentration.Collectively,the results indicate that BaP mainly accumulated in Fraction E,and that the accumulation of BaP in Fraction C and E was correlated with the content of protein and activity of AChE,which was influenced by Cd2+.Furthermore,BaP concentration initially decreased,but subsequently increased,with the increasing concentration of Cd2+.