1992 Volume 27 Issue 1 Pages 30-44
Evaluated a significant enhancement of unscheduled DNA synthesis (UDS) in airway epithelial cells following exposure to diesel exhaust, several in vitro and in vivo experiments were carried out. On the in vivo exposure, F344 SPF rats were divided into three groups according to the content of exhaust; the whole-exhaust exposure (WE) group, the filtered-exhaust exposure (FE) group, and clean air exposure (control) group. After one month of exposure, no significant difference in the mean number of grains per UDS positive cell (G/N) was observed among the three groups. After 6 months exposure, significant increase of UDS was noted in the tracheal epithelium of WE group as compared to FE and control groups.
The maximal UDS in G/N was observed at 6 months of exposure, showing three times higher value than the other two groups. There was no significant difference between FE and control groups over the whole exposure period. It suggested that the particle and its content, butnot the gaseous component, play an important role in UDS. Normal cell division was not affected by diesel particle exposure. The bronchiolar epithelium exposed to WE for 12 months also indicated a significantly higher UDS value than the control group.
Then, various concentration of diesel exhaust particle (DEP) were added to the culture medium, and UDS was estimated on the rat tracheal epithelial cells. Augmented, dose-dependent UDS rate was also observed under in vitro exposure of DEP to the rat tracheal epithelia.
When dilluted benzene-ethanol extract of DEP was added to the culture medium for the rat tracheal epithelia and the human bronchial cells which were obtained surgically, UDS rate increased in both the rat and the human. Scheduled cell division in the rats were seen morefrequently than those in the humans.
Our data demonstrated that DEP are an inducible substrate for UDS to both the rat tracheal epithelium and the human bronchial epithelium.
