挥发性甲基硅氧烷的体外代谢行为

挥发性甲基硅氧烷(volatile methyl siloxanes,VMSs)的高产量、环境广泛存在性和毒性使其成为备受关注的新型环境污染物.VMSs在生物体中的代谢速率是决定其生物富集性的关键因子,但是目前还没有此类物质代谢速率的测试和报道.利用了鲈鱼和鹌鹑肝微粒体的体外代谢体系,测定了16种常见VMSs(D3~D6和L3~L14)的固有清除率.VMSs在鲈鱼肝微粒体中的固有清除率为0~0.031 m L·(h·mg)-1.D5在鲈鱼肝微粒体中难以代谢,与其在水生食物网中呈现显著生物放大性相一致;L4~L14均难以代谢,表明链状VMSs可能具有较高的生物富集性.VMSs在鹌鹑肝微粒体中的固有清除率0.25~1.7m L·(h·mg)-1]显著高于鲈鱼,较快的代谢速率表明D3~D6和L3~L14在鸟类中可能不存在明显的生物放大现象;应用Ba]P作为基准物质校正代谢速率的测定误差,分析VMSs代谢速率的构效关系,发现影响VMSs在鸟类肝微粒体中代谢速率的主要因素为疏水性和电性参数.

In vitro Metabolism of Volatile Methyl Siloxanes

Volatile methyl siloxanes (VMSs) are of great concern in the past few years due to their high production volume, ubiquitousness in the environment and toxicities. The bioaccumulation of VMSs is reported to be sensitive to their metabolism rates, however, little is known about their metabolic rates in aquatic organisms. The present study measured intrinsic clearance rates of 16 common VMSs (D₃-D₆ and L₃-L₁₄) incubated in liver microsomes of weever and quail. The intrinsic clearance rates of VMSs in weever microsomes were 0-0.031 mL·(h·mg)^-1. The fact that D₅ exhibited no significant decline trend in the incubations with liver microsomes of weever corresponded with its trophic magnification behaviour in aquatic food webs. L₄-L₁₄, similar to D₅, were also persistent in microsomes, suggesting the high bioaccumulation potentials of the chemicals. The intrinsic clearance rates of VMSs incubated in quail microsomes 0.25-1.7 mL·(h·mg)^-1] were significantly higher than those incubated in weever microsomes. The relatively high biotransformation rates of D₃-D₆ and L₃-L₁₄ suggested that these compounds may not exhibit high biomagnification potentials in birds. Ba]P was used as a benchmark chemical to normalize variations in determining the metabolism rates among batches, and the structure-activity relationships were explored for the normalized intrinsic clearance rates of quail microsomes. Hydrophobicity and electric properties were found to be major factors influencing the bird microsomal intrinsic clearance rates of VMSs.