Effects of toluene on platelet membrane glycoprotein Ib and actin-binding protein

Effects of the organic solvent toluene on the platelet membrane receptor glycoprotein Ib (GP Ib) and the cytoskeletal protein, actin-binding protein (ABP), were studied and related to the effects of the local anesthetic dibucaine. The glycocalicin-region of GP Ib contains the binding site for von Willebrand factor; intracellularly GP Ib is linked to the cytoskeleton via ABP. Both GP Ib and ABP are substrates for a calcium-dependent protease, calpain. Washed platelets were incubated with toluene or dibucaine. The toluene concentration in the platelet suspension was analysed by gas chromatography. Using 1.5-2.8 mmol/L toluene, calpain was activated, leading to degradation of ABP and release of glycocalicin from GP Ib. The latter phenomenon was paralleled by a reduced von Willebrand factor-induced platelet agglutination. At lower toluene concentrations (0.3-1.4 mmol/L), degradation of ABP was not detected but an initial increased agglutination that declined to the control level with time was observed. These effects of toluene on the GP Ib-ABP complex are similar to those observed with 1 mmol/L dibucaine. The lowest toluene concentrations used correspond to those that have been found in blood from toluene abusers ("sniffers").