MIP-2 response and cell death in rat alveolar macrophages after exposure to quartz particles of different sizes and to amorphous microsilica. The macrophages were exposed to quartz (≤ 0.5 μm, ≤ 2.0 μm, ≤ 10 μm) and microsilica (≤ 0.3 μm) for 20 h as described in Materials and Methods. A, B: MIP-2, concentration-effect curve. C, D: Cell viability, concentration-effect curve. E, F: Apoptosis, concentration-effect curve. In A, C, E the data are related to the mass of the particles, and in B, D, F to the surface area of the particles. The MIP-2 responses were analysed by ELISA. The cell viability was measured by exclusion of PI in a fluorescence microscope. The apoptosis was analysed by flow cytometry after staining by Hoechst 33258. The results represent the mean +/- SEM of three independent experiments.