MODULATION OF BIOCHEMICAL AND CYTOLOGICAL PROFILE OF BRONCHOALVEOLAR LAVAGE CONSTITUENTS IN RATS FOLLOWING SPLIT-DOSE MULTIPLE INHALATION EXPOSURE TO METHYL ISOCYANATE

1 Studies were carried out to explore the acute pulmonary effects of e qual, split-dose, multiple inhalation exposures of rats to methyl isoc yanate (MIC), (0.32 mg l-1, 8 min x 10 exposures) as reflected by alte rations in bronchoalveolar lavage fluid (BALF) constituents and to eva luate recovery, if any, following survival in a MIC-free environment, 10 d after the last MIC exposure. 2 In the BALF of MIC-exposed rats, t here was an increase in the total number of cells and the number of ce lls showing enhanced dye uptake and reduction of nitroblue tetrazolium chloride. The cell-free BALF showed increases in total protein, siali c acids and lactic acid contents and lactate dehydrogenase activity. 3 In rats exposed to MIC and sacrificed 1 0 d after survival in a MIC-f ree environment, there was a reduction in the cellular and biochemical constituents of BALF, The phagocytic potential of macrophages was, ho wever, also decreased under this regime.