Pulmonary intravascular macrophages: their contribution to the mononuclearphagocyte system in 13 species

The organ uptake of intravenously injected particles was examined in 13 spe cies. All animals were injected intravenously with Au-198 colloid and magne tic iron oxide particles. Vascular clearance kinetics of Au-198 colloid was Similar in all species. Pulmonary uptake of Au-198 colloid ranged from 17 to 60% in sheep, calves, pigs, and cats but was <1.1% in monkeys, hyraxes, rabbits, guinea pigs, rats, mice, and chickens. For iron oxide particles, p ulmonary uptake ranged from 80 to 99% in sheep, calves, pigs, goats, and ca ts and 15 to 18% in hamsters, hyraxes, and monkeys and was <10% in rabbits, chicken, mice, rats, and guinea pigs. In all species, the bulk of the rema inder of particle uptake was in the liver. Pulmonary intravascular macropha ges are the cellular site of lung uptake in calves, cats, pigs, goats, and sheep, whereas monocytes and neutrophils predominate in other species. Kupf fer cells were the site of uptake in the liver. Our data show marked specie s differences in the fate of circulating particles; ruminants, pigs, and ca ts have extensive pulmonary localization due to phagocytosis by pulmonary i ntravascular macrophages.