三聚氰胺在罗非鱼肝脏内的累积及对EROD和GST活性的影响

以吉富罗非鱼（Oreochromis niloticus）作为研究对象，采用室内水族箱模拟水生态系统，研究了20 d试验期内，水体中初始质量浓度为0.05 g L-1的三聚氰胺在罗非鱼肝脏中的累积规律及不同暴露时间，对罗非鱼肝脏中7-乙氧基-异酚噁唑酮-脱乙基酶（EROD）和谷胱甘肽-S-转移酶（GST）活性的影响。结果表明：随着试验时间的延长，三聚氰胺在罗非鱼肝脏中的质量分数先迅速上升，在第2天高达4.15 mg·kg-1。随后逐渐下降，在第20天降至0.8 mg·kg-1，恢复到暴露初期水平。与对照组相比，罗非鱼肝脏中EROD和GST的活性在第1天被轻微诱导之后，分别在第2天和第4天开始被显著抑制，抑制率分别为50.7%和69.4%。随后两者的活性上升并分别在第7天和第10天开始被显著诱导，诱导率各为122.9%和47.7%。总体上看，EROD和GST的活性皆呈现出诱导-抑制-诱导的变化趋势。但在暴露结束时，这两种酶的活性又显著低于对照组，抑制率分别为34.1%和20.3%。结果显示，罗非鱼肝脏中EROD酶和GST酶，在一定程度上可作为水体中三聚氰胺污染的生物监测指标。

Accumulation of melamine in tilapia liver and its effect on EROD and GST activities

The bioaccumulation of melamine in the liver of tilapia（Oreochromis niloticus）and its effect on the activities of 7-ethoxyresorufin-O-deethylase （EROD） and glutathione S-transferase（GST）at various exposure time were investigated with a stimulated aquatic micro-system, during a 20 days trial period with initial melamine concentration of 0.05 g·L-1 in water. It was found that melamine could be absorbed quickly in the liver at the initial exposure stage, and its concentration reached the highest value of 4.15 mg·kg-1 at the 2nd day of exposure. With the increase of exposure time, the melamine residue in the liver decreased gradually. After 20 treated days, the melamine concentration was reduced to 0.8 mg·kg-1, resuming the level at the early stage of exposure. The analytical results indicated that compared with the control group, the EROD and GST activities in the treated group were slightly induced at the first day exposure, then significantly inhibited by 50.7%for EROD at the 2nd day and 69.4%for GST at the 4th day, respectively. Thereafter, pronounced inducements were observed in EROD activity by 122.9%at the 7th day, and in GST activity by 47.7% at the 10th day. In general, the activities of both enzymes followed a change tendency of inducement, inhibition, and inducement again with an increase of exposure time. At the end of the test period, the EROD activity and GST activity revealed obvious decrease with inhibition rates of 34.1%and 20.3%respectively. The results in the present work showed that EROD and GST may act as biomarkers for indicating melamine pollution in aquatic environment.