IN-VITRO CALCIUM AND CALMODULIN-DEPENDENT KINASE-MEDIATED PHOSPHORYLATION OF RAT-BRAIN AND SPINAL-CORD NEUROFILAMENT PROTEINS IS INCREASED BY GLYCIDAMIDE ADMINISTRATION

This study was carried out to determine the action of glycidamide (2,3 -epoxy-1-propanamide), a neurotoxic metabolite of acrylamide, on Ca2+/ calmodulin (CaM)-dependent protein kinase phosphorylation of cytoskele tal proteins. Acrylamide has been shown to increase Ca2+/CaM-dependent phosphorylation of neurofilament (NF) triplet proteins and autophosph orylation of Ca2+/CaM-dependent protein kinase II (CaM kinase II; EC 2 .7.1.37), A daily intraperitoneal dose of 0.7 mmol/kg b.wt. of glycida mide or deionized water was administered to male Sprague-Dawley rats. Animals were sacrificed when signs of severe neurotoxicity became appa rent at 13-16 days of treatment. Axonal floatation was used to isolate neurofilaments (NFs) and endogenous kinases from brains and spinal co rds of treated and control animals. Samples isolated from brain and sp inal cord of glycidamide-treated animals showed increased in vitro Ca2 +/CaM-dependent phosphorylation of endogenous and exogenous NF protein s and increased autophosphorylation of CaM kinase II when compared wit h controls. CaM binding to the alpha, beta, and beta' subunits of CaM kinase II and antibody binding to the alpha-subunit of CaM kinase II i n brain supernatant isolates was increased as a result of glycidamide treatment. These results suggest that increased Ca2+/CaM-dependent pho sphorylation of cytoskeletal proteins may be involved in the pathogene sis of glycidamide-induced neurotoxicity.