When the phagocytic response of pulmonary cells obtained from rat lung lavage to insoluble particles was assessed in an in vitro system under conditions of selected variables, a peak phagocytic response occurred for most metal oxides (except Fe2O3) at 10-4 M Ca++ and at 10-7 M UO2++ in a simple saline medium. The Ca++ effect was interrelated with particle concentration for SiO2 particles. Phagocytic response increased with particle to cell ratios up to 10 to 15 with several particle species. These and other data including enhanced phagocytosis with poly-L-lysine, are discussed in relation to peritoneal cell responses, charge characteristics of particles, and the implications of the findings to in vivo lung responses.
Casarett LJ, Casarett MG, Whalen SA. Pulmonary Cell Responses to Metallic Oxides. Arch Intern Med. 1971;127(6):1090-1098. doi:10.1001/archinte.1971.00310180106015