Passage of Intratracheally Instilled Ultrafine Particles from the Lung into the Systemic Circulation in Hamster

The mechanisms of particulate pollution-related cardiovascular morbidity and mortality are not well understood. We studied the passage of radioactively labeled ultrafine particles after their intratracheal instillation. Hamsters received a single intratracheal instillation of 100 μ g albumin nanocolloid particles (nominal diameter ⩽ 80 nm) labeled with 100 μ Ci technetium-99m and were killed after 5, 15, 30, and 60 min. In blood, radioactivity, expressed as percentage of total body radioactivity per gram blood, amounted to 2.88 ± 0.80%, 1.30 ± 0.17%, 1.52 ± 0.46%, and 0.21 ± 0.06% at 5, 15, 30, and 60 min, respectively. Thin-layer chromatography showed only one peak of radioactivity corresponding to unaltered 99mTc-albumin nanocolloid. In the liver, radioactivity, expressed as percentage of total radioactivity per organ, amounted to 0.10 ± 0.07%, 0.23 ± 0.06%, 1.24 ± 0.27%, and 0.06 ± 0.02% at 5, 15, 30, and 60 min, respectively. Lower values were observed in the heart, spleen, kidneys, and brain. Dose dependence was assessed at 30 min following instillation of 10 μ g and 1 μ g 99mTc-albumin per animal (n = 3 at each dose), and values of the same relative magnitudes as after instillation of 100 μ g were obtained. We conclude that a significant fraction of 99mTc-albumin, taken as a model of ultrafine particles, rapidly diffuses from the lungs into the systemic circulation.