Objective: To compare the determination ability of four in vitro cytotoxicity assays for acute toxicity of diesel exhaust particulate (DEP) extracts.
Method: The cell viability of cultured 16HBE cells was measured by the MTT assay, the neutral red assay, the lactate dehydrogenase (LDH) leakage assay and the determination of total protein content after 12, 24 and 48h of being exposed to DEP extracts at different concentrations of 5, 10, 20, 40, 80 and 160 microg/ml.
Results: For measuring the acute cytotoxicity, the MTT assay was more delicate than the other three methods after 12h exposure. The sensitivity of both the MTT assay and the neutral red assay increased as the exposure time extended. The cell viability at each dosage decreased significantly after being exposed to DEP extracts for 24h compared to the control group (P < 0.05). When using the LDH assay, the cell viability reduced after 24h exposure to DEP extracts, but changed no more as time prolonged. Only the cell viabilities of the groups exposed to the high dosages of DEP extracts were observed with significant reduction by the protein assay after 12h and 24h exposure respectively. The cell viabilities measured by the same method at all dosages decreased after 48h exposure.
Conclusion: The results of the four cytotoxicity assays showed differences in the present study. The MTT assay and the neutral red assay are more sensitive in detecting the adverse effect to 16HBE cells done by DEP extracts compared to the LDH assay and the protein assay. Taken the indicants of each toxicity assay into account, the DEP extracts may have major adverse effects on the functions of the organelles in 16HBE cells, such as mitochondria and lysosomes, however little influence to the cell anchorage dependence and the cell membrane damage.