4-WEEK EXPOSURE TO DIESEL EXHAUST INDUCES NASAL MUCOSAL HYPERRESPONSIVENESS TO HISTAMINE IN GUINEA-PIGS

It has been reported that diesel exhaust (DE) particulates augment inc reases in nasal congestion and nasal secretion induced by histamine (H is). We also showed that short-term (3-h) exposure to DE induces nasal mucosal hyperresponsiveness to His. Therefore, in the present study w e investigated that whether 4-week exposure of guinea pigs to diesel e xhaust would likewise induce nasal mucosal hyperresponsiveness to His. Sneezing number, nasal secretion from the nostril, and intranasal air way resistance induced by His were measured as indices of sneezing res ponse, rhinorrhea, and nasal congestion, respectively. Guinea pigs of each group were exposed to filtered air, with or without a low or high concentration of DE for 3, 7, or 28 days. Exposure to a low or high c oncentration of DE itself did not induce sneezing, nasal secretion, or nasal congestion. However, exposure to a high concentration of DE aug mented that the number of sneezes induced by His, whereas exposure to a low concentration of DE had no significant effect. Exposure to DE fo r 7 and 28 days tended to augment an increase in nasal secretion induc ed by exposure to His aerosol in a DE concentration-dependent fashion. The augmentation, however, was not statistically significant. Exposur e to high or low DE for 3 or 7 days had no significant effect on the i ncrease in intranasal pressure (INP) induced by a 10-min exposure to H is aerosol, but exposure to high DE for 28 days augmented the increase in INP induced by His, significantly. Exposure to low DE for 28 days did not augment the increase in INP immediately after inhalation of Hi s aerosol. These results reveal that 4-week exposure to high DE induce s nasal mucosal hyperresponsiveness in guinea pigs, (C) 1998 Society o f Toxicology.