Evaluation of the neurotoxicity of glycidamide, an epoxide metabolite of acrylamide: behavioral, neurochemical and morphological studies

Acrylamide is an important chemical used in the synthesis of polyacrylamides, which have a wide variety of industrial applications. The principal toxic effect of acrylamide, both in animals and in humans, is neurotoxicity. Peripheral nervous system effects are most prominent, but central nervous system effects have also been reported. Acrylamide is metabolized to the epoxide glycidamide, whose adducts to hemoglobin and to DNA have been identified in animals and humans. This metabolite may be involved in the reproductive and carcinogenic effects of acrylamide. In the present study we investigated whether glycidamide would exert neurotoxic effects similar to those caused by its parent compound. Male rats were injected i.p. with acrylamide (25 or 50 mg/kg) or glycidamide (50 or 100 mg/kg) daily for 8 days. Reduced weight gain was evident in animals exposed to glycidamide or to the higher dose of acrylamide. Both compounds induced lethargy and ataxia, but the posture of glycidamide-treated rats differed from that of animals treated with acrylamide. At the high doses, both compounds significantly affected rats' behavior in the rotarod test; on the other hand, only acrylamide was effective in the hindlimb splay test. Acrylamide inhibited activity of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in sciatic and tibial nerves, as well as in brain. Glycidamide inhibited GAPDH activity only in brain and activity of creatine kinase in both peripheral and central tissues. Acrylamide also caused profound urinary retention and distended bladders, while the effects of glycidamide were minimal. Morphological abnormalities were seen in sciatic nerves and dorsal root ganglion cells of rats treated with acrylamide (50 mg/kg x 12), but not in rats exposed to glycidamide (100 mg/kg x 11). These results indicate that the toxicities of acrylamide and glycidamide differ and suggest that acrylamide itself may be primarily responsible for its peripheral neurotoxicity.