镉对苯并(a)芘在蚯蚓亚细胞组分中分配积累的影响

Effects of cadmium on the distribution and accumulation of benzo [a] pyrene in subcellular fractions of Eisenia fetida

通过外源添加不同浓度镉离子(Cd^(2+))来研究复合污染条件下镉(Cd)对苯并(a)芘(Ba P)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,Ba P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Cd^(2+)添加处理下,随着Cd^(2+)浓度的增加,3个细胞组分中的Ba P浓度呈先降低后升高的趋势。随着Cd^(2+)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(ACh E)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Ba P浓度呈显著负相关;细胞溶质组分中的ACh E活性与该组分中的Ba P浓度呈显著负相关;而GST的活性与Ba P浓度没有显著相关性。综上所述,Ba P主要分配积累在细胞碎片组分中,Cd^(2+)可能通过影响蛋白含量及ACh E的活性,从而影响Ba P在细胞碎片和细胞溶质组分中的积累,使得Ba P的浓度随着Cd^(2+)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＋.