INCREASES IN THE MESSENGER-RNA LEVELS OF GAMMA-GLUTAMYL-TRANSFERASE AND HEME OXYGENASE-1 IN THE RAT LUNG AFTER OZONE EXPOSURE

gamma-Glutamyltransferase (GGT) and heme oxygenase-1 (HO-1) are induce d by chemical and physical stresses producing an oxidative burden on t issues and cells. Both enzymes are proposed to have an antioxidant rol e in protecting cells and tissues from oxidative burden. To explore th e effects of ozone (O-3), the major oxidant in photochemical smog, on the expression of GGT and HO-1 genes in the lung, we exposed rats to 0 .4 ppm O-3 for up to 7 days. After exposures, mRNA levels of GGT and H O-1 in the lung were measured by RNA blot analysis. Although a 1-day e xposure did not change either GGT or HO-1 mRNA levels in the lung, bot h genes responded to prolonged exposure to O-3. GGT mRNA was increased to 149% (P < 0.01) and 158% (P < 0.01) of the control by 3- and 7-day exposures, respectively. HO-1 mRNA was also elevated to 174% (P < 0.0 1) and 184% (P < 0.001) of the control after 3- and 7-day exposures, r espectively. The elevation of GGT and HO-1 mRNA after prolonged exposu re to O-3 suggests that expression of these genes is not involved in t he acute respiratory response, but in the recovery process from lung d amage induced by O-3. (C) 1997 Elsevier Science Inc.