栉孔扇贝对氮杂螺环酸毒素代谢解毒的生理应激响应

PHYSIOLOGICAL RESPONSE OF SCALLOP CHLAMYS FARRERI TO THE METABOLIC DETOXIFICATION OF AZASPIRACIDS

将栉孔扇贝(Chlamys farreri)暴露于分离自我国近海的一株氮杂螺环酸毒素(azaspiracids,AZAs)产毒藻——腹孔环胺藻(Azadinium poporum,AZDY06株,主产AZA2),研究了栉孔扇贝对AZAs的代谢解毒效应以及代谢过程中血细胞数量、抗氧化酶活性及细胞超微结构变化等生理应急响应。结果发现,栉孔扇贝对AZDY06所产的AZA2具有一定的代谢解毒能力,可将AZA2转化成AZA6、AZA12、AZA19和AZA23等4种极性较强且毒性较低的代谢产物。代谢解毒过程中,栉孔扇贝血细胞数量、关键抗氧化酶活性及靶器官细胞超微结构均出现一定的应激效应,且总体表现出明显的剂量-效应关系。栉孔扇贝血细胞数量对AZAs表现出较强的应激反应,且随实验过程出现较大波动,最高可达对照组的2—3倍;抗氧化系统酶如超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-Px)、过氧化物酶(POD)和酸性磷酸酶(ACP)活性也出现不同程度的变化:GSH-Px与POD在整个蓄积代谢过程中均表现出持续激活状态,且血液中这两种酶活性最高,可达内脏和鳃中的20倍以上;SOD活性与扇贝中AZAs含量有一定关系,AZAs含量为74.2—168.2μg AZA1 eq/kg时为诱导状态,过高或过低剂量均表现为抑制效果;而ACP对AZAs的应激表现也十分敏感,但代谢过程中大部分时间为被持续抑制状态。此外,AZAs还导致栉孔扇贝内脏和鳃细胞超微结构出现空泡化、核固缩等病理性变化;实验后期,低暴露组细胞结构出现一定的自我修复现象,而高暴露组则无此现象。本研究可为进一步深入探索AZAs的解毒机制,对其进行风险评价并制定限量标准提供科学依据。

To understand the physiological response of scallop Chlamys farreri to the metabolic detoxification of azaspiracids(AZAs),the scallop was exposed to a toxic algae of AZAs,Azadinium poporum(strain AZDY06,producing AZA2 mainly,isolated from the South China Sea).Except for the metabolic process of AZAs in scallop,activities of four enzymes including superoxide dismutase(SOD),glutathione peroxidase(GSH-Px),peroxidase(POD),and acid phosphatase(ACP)in the blood,viscera,and gills,as well as the total hemocyte counts(THC)were measured.In addition,the ultrastructure of viscera and gill cell were observed to study the structural damage.The results show that C.farreri could convert AZA2 into four metabolites(AZA6,AZA12,AZA19,and AZA23)that have strong polarity and low toxicity,which means that C.farreri could protect itself by eliminating the toxicity of AZAs.However,some physiological parameters,including THC,activities of key antioxidant enzymes,and the ultrastructure of target organ cells,also showed responding reaction during the detoxification process,and some of these parameters showed obvious dose-effect relationship.The THC fluctuated greatly to the highest level of 2—2.5 times of the control group’s.The activities of four antioxidant enzymes changed to different degrees.GSH-Px and POD were activated continuously during the whole process,especially in blood,more than 20 times of those in viscera and gills.The SOD activity showed a strong relationship with AZA content.When the AZAs content was in 74.2—168.2μg AZA1 eq/kg,SOD activity was in the induction state,and otherwise in inhibitory state below or beyond the range.Different from other enzymes,the ACP activity was inhibited in almost of all the process.In the ultrastructure,some pathological phenomena such as vacuolization and nuclear atrophy occurred in the cells of viscera and gill.The tissue cells in low-exposure group could self-repair their structure to some degrees,but not in high-exposure group.This study provides a scientific basis for future study of the detoxification mechanism of AZAs,as well as the risk assessment and limit setting of this phycotoxins in standard.