INHIBITION OF CATALASE ACTIVITY IN-VITRO BY DIESEL EXHAUST PARTICLES

The effect of diesel exhaust particles (DEP) on the activity of catala se, an intracellular antioxidant, was investigated because H2O2 is a c ytotoxic oxidant, and catalase released from alveolar cells is an impo rtant antioxidant in the epithelial lining fluid in the lung. DEP inhi bited the activity of bovine liver catalase dose-dependently, to 25-30 % of its original value. The inhibition of catalase by DEP was observe d only in the presence of anions such as Cl-, Br-, or thiocyanate. Oth er anions, such as CH3COO- or SO4-, and cations such as K+, Na+, Mg2+, or Fe2+, did not affect the activity of catalase, even in the presenc e of DEP extract. Catalase from guinea pig alveolar cells and catalase from red blood cells were also inhibited by DEP extracts, as was cata lase from bovine liver. These results suggest that DEP taken up in the lung and located on alveolar spaces might cause cell injury by inhibi ting the activity of catalase in epithelial lining fluid, enhancing th e toxicity of H2O2 generated from cells in addition to that of O-2(-) generated by the chemical reaction of DEP with oxygen.