镉对单环刺螠非特异性免疫及组织蓄积的影响

为探究镉(Cd)对海洋动物的毒性效应,考察了不同质量浓度(0.005、0.05和0.5 mg·L~(-1)) Cd处理对单环刺螠相关免疫生理指标及主要组织中Cd蓄积量的影响。结果表明:Cd胁迫下,血细胞密度(density of hemocyte, DHC)先升后降再升,酚氧化酶(phenoloxidase, PO)活力先升后降,溶菌酶(lysozyme, LSZ)活力先降后升再降,至处理96 h,处理组DHC均显著高于对照组(P0.05),总蛋白含量变化不显著;除低浓度胁迫组(0.005 mg·L~(-1))PO活力与对照组相近外,其他处理组的PO和LSZ活力均显著低于对照组(P0.05)。超氧化物歧化酶(superoxide dismutase, SOD)活力和丙二醛(malondialdehyde, MDA)含量总体呈上升趋势,过氧化氢(H_2O_2)含量先升后降再升,至胁迫96 h,各处理组SOD活力、MDA和H_2O_2含量均显著高于对照组(P0.05)。总之,Cd胁迫对单环刺螠非特异性免疫影响显著,Cd的短期胁迫可刺激DHC、PO和LSZ升高,免疫力增强,而高浓度Cd的胁迫时间较长会造成机体解毒能力下降,持续刺激机体产生过氧化反应,MDA含量升高,可作为单环刺螠在Cd长期胁迫下的免疫检测指标。不同胁迫浓度组单环刺螠肌肉和消化道中的Cd含量随胁迫时间均呈上升趋势,且存在显著的时间-剂量-效应关系(P0.05),其蓄积量水平为:消化道肌肉,具有组织特异性。

Effects of Cadmium on Non-specific Immunity and Bioaccumulation of Urechis unicinctus

In this study, the effects of various concentrations of cadmium (Cd) on non-specific immunity indexes, its bioaccumulation and toxicity in the tissues of Urechis unicinctus were investigated. Results show that the density of hemocyte (DHC) initially increased, then decreased before increasing again under Cd stress. In addition, the activity of phenoloxidase (PO) was found to be increased initially and then decreased, while lysozyme (LSZ) activity increased after initial decrement and then decreased. After treatment of 96 h, DHC of the treatments was found to be significantly higher than control group (P<0.05), with no significant change in total protein content. PO activity under low Cd concentration (0.005 mg L^-1) was similar to the control group. In contrast, PO and LSZ activities of other treatments were significantly lower than control. While, superoxide dismutase (SOD) activity and malondialdehyde (MDA) content increased continually, H₂O₂ content was found to be decreased after initial increment before increasing again. SOD activity, MDA and H₂O₂ content in treatments were significantly higher than control group (P<0.05) after 96 h of Cd stress. In conclusion, Cd stress exhibited significant effect on non-specific immunity of U. unicinctus. After being subjected to short-term of Cd stress, some immunity indexes, including DHC, and the activities of PO and LSZ were found to be increased, indicating improved immunity. However, long-term exposure of higher Cd concentration led to the decrease of detoxification ability and thus stimulated the body to undergo peroxidation. This led to the increase in MDA content that could be used as an immunoassay indicator of U. unicinctus under long-term Cd stress. Cd content in the muscle and digestive tract of U. unicinctus were found to be increasing with the prolongation of stress time, exhibiting significant time-dose-effect relationship (P<0.05). Moreover, the accumulation of Cd in U. unicinctus showed tissue specificity, with significantly higher Cd content in digestive tract when compared to that of muscle.