[Study on the morphological damage and cell apoptosis of nerve tissue in mice exposed to benzo[a]pyrene].

OBJECTIVE: To study the toxicological effects of benzo[a]pyrene(BaP) on mammalian animal's nerve tissue. METHODS: 50 Kunming mice were divided into 5 groups at random, the exposed groups(3 dose level groups), the vehicle control group and standard control group. Every group got 10 mice. The exposed groups were treated by intraperitoneal injection with BaP dissolved in vegetable oil at 7.8, 3.2 and 1.3 mg/kg respectively, 4 times/week, for 10 weeks, the vehicle control group were given vegetable oil and the standard control group were not given any treatment. All the mice were anesthetized with 0.02 mol/L pentobarbital and infused with 1.33 mol/L paraformaldehyde dissolved in PBS through heart after 10 weeks. Then the brain, spinal cord and sciatic nerve were removed. Slices of these tissues were made and morphological changes were observed by optical microscope and electron-microscope. Cell appoptosis was examined by TUNEL(TdT-mediated x-dUTP nick end labeling) method. RESULTS: Morphological observations showed tissue injury in BaP exposed groups. There were focal necrosis areas found in the high-dose group. The cell apoptosis rates in 3.2 and 1.3 mg/kg groups were 90.02%-94.22% and 62.45%-77.54% respectively, significantly higher than those of vehicle control group and standard control group(4.60%-5.57%). CONCLUSION: BaP is neurotoxic. It could damage the nerve tissue as well as induce DNA breaks and cell apoptosis.