Silica Induced Alveolar Leucocytosis: Modulation by Mepacrine

The initial response of the lung to inhalation of many dusts frequently includes the mobilization of polymorponuclear leucocytes (PMN) into the alveolar spaces. Lugano et al. (1982) demonstrated such a response following intra-tracheal instillation of silica particles in guinea pigs. The response occurred within the first 24 hours and was followed by fibrosis at the seventh post-instillation day. We used a somewhat similar model employing adult Fisher 344 rats which received 0.5 mg of autoclaved endotoxin free Minusil in 0.35 ml of saline by the intratracheal route-a full report is now published (Mikes, P.S., et al. 1988a). Briefly this model showed that broncho-alveolar lavage (BAL) fluid showed a twofold increase in cell yield, of which 35% were PMN. This contrasts with the 1% PMN yield in control animal BAL fluid. This represents a 200 fold increase in the number of lavage recovered PMN. The PMN response was not accompanied by much increase in either total protein or albumin concentration in the BAL fluid from silica treated animals, thus no great inflammatory response occurred at least as judged by this measure of capillary permeability.