CYTOTOXICITY OF AMBIENT AIR PARTICLES TO RAT LUNG MACROPHAGES - COMPARISON OF CELLULAR AND FUNCTIONAL ASSAYS

The biological reactivity of ambient air particles was studied in five in Ditro lung macrophage assays, involving the release of cytoplasmic and lysosomal enzymes, cellular ATP, neutral red uptake, tetrazolium reduction, and chemiluminescence. Macrophages from rat lungs (2 x 10(5 ) cells; 1 cm(2) attachment surface; 1 mi culture medium) were exposed for 18 hr to 0-100 mu g of (1) the urban dust SRM 1649, (2) titanium dioxide (TiO2()) or (3) DQ-12 quartz. On the basis of the depressions of neutral red uptake and cellular ATP, and the extracellular releases of lactate dehydrogenase, acid phosphatase and beta-glucuronidase, th e ranking of cytotoxicity was as follows: quartz (EC(50) = 20-60 mu g/ ml) much greater than SRM 1649 approximate to TiO2 (EC(50) > 100 mu g/ ml). The decrease in itro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilid e (XTT) reduction was more sensitive to effects of the urban dust, wit h an EC(50) value for SRM 1649 (35 mu g/ml) intermediate between those for quartz (15 mu g/ml) and TiO2 (82 mu g/ml). Although SRM 1649 coul d affect mitochondrial function, the impact of the urban dust on cellu lar integrity after 18 hr was comparable to that of TiO2 particles. In contrast, SRM 1649 had profound effects on phagocytosis-related chemi luminescence values measured during a 5-hr exposure period. Quartz and TiO2 particles induced an oxidative burst from the macrophages. Howev er, whereas a low dose of SRM 1649 (25 mu g) induced an oxidative burs t, a further increase of the dose of particles (100-250 mu g) resulted in a decrease of the luminol-dependent luminescence (P < 0.05) and, t o a lesser extent, of the lucigenin-dependent luminescence. The data i mply an early adverse effect of ambient air particles on the bacterici dal activity of macrophages with minimal alterations in the structural integrity of the cells. Copyright (C) 1996 Elsevier Science Ltd.