铅、汞单一及联合胁迫对栅藻的生长、GSH含量及相关酶活性的影响

Individual and Joint Stress of Lead and Mercury on Growth,Glutathione and Glutathione-Related Enzymes of Scenedesmus quadricauda

为进一步了解重金属复合污染对水生植物产生毒害作用的机制,以单细胞藻类生长及细胞内还原型谷胱甘肽(GSH)含量、谷胱甘肽-S-转移酶(GST)和谷胱甘肽过氧化物酶(GPx)活性为指标,对铅和汞单一及联合胁迫对四尾栅藻的毒性作用进行了研究.结果表明,铅[Pb(NO3)2]和汞(HgCl2)单一胁迫对四尾栅藻生长抑制的96h EC50分别为0.678 9 mg/L和0.140 1 mg/L,二者的联合作用相加指数AI为0.009,表现为典型的相加作用.经铅、汞单一及联合染毒12 h后,栅藻体内GSH含量降低到对照组的70%左右,并在一定浓度范围内保持水平上的稳定;GST活性随胁迫浓度的增加而先上升后下降,联合染毒高浓度组中甚至出现了明显的活性抑制,抑制率为13.04%;GPx活性整体受到明显抑制并随浓度增加而持续下降,最低值仅为对照组的38.77%.铅、汞联合胁迫对四尾栅藻体内GSH含量、GST及GPx活性的影响也验证了二者之间的联合作用关系为相加作用.

To understand the toxicity mechanisms of mixed heavy metals on aquatic plant, indicators of algea growth rate, content of reduced glutathione （GSH）, activities of glutathione S-transferase （GST） and glutathione peroxidase （GPx） of green algae, Scenedesmus quadricauda were measured to analyze the individual and joint toxic effects of lead and mercury. The results show that the 96h EC50 of algae growth inhibition by lead [ Pb（NO3 ）2 ] and mercury （HgCl2） are 0.678 9 mg/L and 0.140 1 mg/L respectively. After 12 h individual and joint lead and mercury exposure, the content of GSH in alga cells is decreased to about 70% of the level of the control,and keeps a steady level with the increase of the exposure concentration.The GST activities are increased to a peak in lower concentration groups and then decrease with the increase of the exposure concentration. Indeed, the higher concentration of lead and mercury combined-poisoning can inhibit the activities of GST significantly, with 13.04% inhibitory rate. The activity of GPx is almost suppressed continuously with the increase of the exposure concentration, and the lowest aetivity is only 38.77 % of the control. The toxic action of the mixture of Pb and Hg on growth inhibition, GSH content, activities of GST and activities of GPx for Scenedesmus quadricauda are addition.