Delayed neurotoxicity of diisopropylfluorophosphate (DFP): autoradiographic localization of high-affinity [(3)H]DFP binding sites in the chicken spinal cord.

The delayed neurotoxic organophosphate, diisopropylfluorophosphate (DFP) binds with high affinity to membrane-bound proteins from chicken nerve tissues. The autoradiographic distribution of [(3)H]DFP binding sites in spinal cord sections of chicken showed higher concentrations of binding sites in gray matter than in white matter. In the cervical region, fairly high densities of [(3)H]DFP binding sites were found in laminae X and to a lesser extent, in the ventral horn gray matter. To identify the membrane-associated DFP-binding proteins, detergent-solubilized membranes were labeled widi 5-10nM [(3)H]DFP (10pmol/mg protein) for 70 min at 37°C. Gel-exclusion chromatography of the [(3)H]DFP-radiolabeled membranes indicated at least two major radioactive proteins with apparent molecular weights of 150-670 kDa and 40-129 kDa. Although we could not identify the high affinity DFP binding proteins, the autoradiographic experiments clearly demonstrated that the DFP binding proteins localized on gray matter of chicken spinal cord.