TNF-α and MIP-2 mRNA expression in alveolar macrophages after exposure to PD and HPD (100 μg/ml) for 4 h. (A) RT-PCR products of GAPDH, TNF-α and MIP-2 in an ethidium bromide stained agarose gel. Data shown are from four representative experiments. GAPDH were used as normalization control. (B) Densitometric analysis of 4 gels. *p < 0.05 compared with untreated control. #p < 0.05 compared with HPD.