Four-week exposure to diesel exhaust induces nasal mucosal hyperresponsiveness to histamine in guinea pigs.

It has been reported that diesel exhaust (DE) particulates augment increases in nasal congestion and nasal secretion induced by histamine (His). We also showed that short-term (3-h) exposure to DE induces nasal mucosal hyperresponsiveness to His. Therefore, in the present study we investigated that whether 4-week exposure of guinea pigs to diesel exhaust would likewise induce nasal mucosal hyperresponsiveness to His. Sneezing number, nasal secretion from the nostril, and intranasal airway resistance induced by His were measured as indices of sneezing response, 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 concentration of DE itself did not induce sneezing, nasal secretion, or nasal congestion. However, exposure to a high concentration of DE augmented that the number of sneezes induced by His, whereas exposure to a low concentration of DE had no significant effect. Exposure to DE for 7 and days tended to augment an increase in nasal secretion induced by exposure to His aerosol in a DE concentration-dependent fashion. The augmentation, however, was not statistically significant. Exposure to high or low DE for 3 or 7 days had no significant effect on the increase in intranasal pressure (INP) induced by a 10-min exposure to His 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 His aerosol. These results reveal that 4-week exposure to high DE induces nasal mucosal hyperresponsiveness in guinea pigs.