[Toxicological assessment of nanostructured silica. II. Enzymatic, biochemical indices, state of antioxidative defence].

Abstract Nanostructured silica (SiO2) "Aerosil" with the size of the primary nanoparticles (NPs) of 5-30 nm, in the form of ultrasound treated water suspension was administered to rats of 80 ± 4 g initial body weight for the first 30 days by intragastric gavage and then for 62 days with diets consumed in doses of 0.1; 1.0; 10 and 100 mg/kg body weight per day. The control group received vehicle of nanomaterial (NM)--deionized water. There were measured in liver of ani- mals the content of total cytochromes P450 and b5 in the microsomal fraction of liver, activity (Vmax) of microsomal monooxygenases with the mixed func- tion of isoforms CYP1A1, 1A2 and 2B1 on their specific substrates, the activity of conjugating liver enzymes glutathione-S-transferase and UDP-glucuronosyl-transferase in microsomal fraction and cytosol, the total and non sedimentable activity of lysosomal hydrolases (β-glucuronidase, β-galactozydase, arylsulphatase A, B). The content of PUFA's diene conjugates and TBA-reactive substances in the blood plasma and the activity of antioxidative enzymes (glutathionperoxidase, superoxidedismutase, glutathionreductase, katalase) in erytrocytes were estimated. A set of standard biochemical parameters of blood serum was also examined (total protein, albumin, glucose, creatinine, urea, uric acid, activities of hepatic transaminases). The studies revealed changes of a number of molecu lar markers that could be interpreted as unfavorable. These include isoforms of CYP2B1 activity decrease at a dose HM 1-10 mg/kg of body weight, decrease in the serum content of total protein, albumin and glucose levels in a dose range of 0.1-10 mg/kg. These changes were absent at the maximum dose of NM, which did not allow to clearly establish the dose-response. The remaining studied fig ures resided in the normal range or experienced changes that could not be interpreted as toxic.