Synergistic neurotoxic effects of styrene oxide and acrylamide: glutathione-independent necrosis of cerebellar granule cells.

Conjugation with glutathione (GSH) is a mechanism of detoxification of acrylamide (ACR); hence, prior depletion of GSH might be expected to exacerbate ACR's neurotoxicity. GSH levels in female rats were reduced by ip administration of styrene oxide (SO; 250 mg/kg), diethylmaleate (DEM; 0.5 ml/kg), or 2-vinylpyridine (VP; 100 mg/kg) 1.5 or 2 hr prior to a single dose of ACR (100 mg/kg). The time course of GSH depletion following treatment with SO/ACR, DEM/ACR, or VP/ACR showed that all three regimens were equally effective in reducing GSH in liver, cerebellum, cerebral cortex, and hippocampus. GSH levels in the liver were reduced to 4-22% of control levels between 2 and 4 hr after treatment and to 38-57% of control levels in all brain regions between 4 and 8 hr. ACR alone (100 mg/kg) reduced both brain and liver GSH to about 60% of normal. The administration of a second dose of ACR (also 100 mg/kg) 12 hr later further depleted brain and liver GSH to 33% of control. Brains were examined 2, 4, 7, 14, and 30 days after treatment by light and electron microscopy. The administration of SO plus ACR (in either order) produced lesions consisting of pyknotic granule cells confined to the anterior portions of the cerebellum and some of the small neurons of lamina II and III of the cerebral cortex. Electron microscopy revealed condensation of the granule cell chromatin and dissolution of the cytoplasm with the formation of large pericellular spaces. The granule cell lesion was not produced when the time between SO and ACR injections was either 4 or 24 hr. No pathology was observed following treatment with DEM/ACR, VP/ACR, ACR/ACR, vehicle (peanut oil), SO, or ACR alone. It appears that the neurotoxicity in animals treated with SO plus ACR is not directly the result of reduced cellular GSH levels per se, but may involve other detoxification pathways of ACR and SO.