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

TLDR

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 µg albumin nanocolloid particles (≤ 80 nm) labeled with 100 µCi technetium‑99m and were sacrificed at 5, 15, 30, and 60 min to assess blood and organ radioactivity. Radioactivity in blood peaked at 2.88 % of total body activity per gram at 5 min and declined thereafter, with only unaltered 99mTc‑albumin detected, and similar dose‑dependent patterns were observed, indicating that a significant fraction of ultrafine particles rapidly enters systemic circulation.

Abstract

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.