Passage of intratracheally instilled ultrafine particles from the lung into the systemic circulation in hamster

The mechanisms of particulate pollution-related cardiovascular morbidity an d mortality are not well understood. We studied the passage of radioactivel y labeled ultrafine particles after their intratracheal instillation. Hamst ers received a single intratracheal instillation of 100 mug albumin nanocol loid particles (nominal diameter less than or equal to 80 nm) labeled with 100 mu Ci technetium-99m and were killed after 5, 15, 30, and 60 min. In bl ood, 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 chromatog raphy showed only one peak of radioactivity corresponding to unaltered Tc-9 9m-albumin nanocolloid. In the liver, radioactivity, expressed as percentag e 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, respectiv ely. Lower values were observed in the heart, spleen, kidneys, and brain. D ose dependence was assessed at 30 min following instillation of 10 mug and 1 mug Tc-99m-albumin per animal (n = 3 at each dose), and values of the sam e relative magnitudes as after instillation of 100 mug were obtained. We co nclude that a significant fraction of Tc-99m-albumin, taken as a model of u ltrafine particles, rapidly diffuses from the lungs into the systemic circu lation.