Radiation-Induced Pulmonary Fibrosis: Study of Changes in Collagen Constituents in Different Lung Regions of Beagle Dogs after Inhalation of Beta-Emitting Radionuclides

Abstract

Pulmonary collagen turnover (synthesis, degradation, and accumulation) was studied in 40 dogs injured by inhalation exposure to ${}^{90}{\rm Y}$ ( $T_{{\textstyle\frac{1}{2}}}{\rm eff}$ 2.6 days, Ē = 0.9 MeV), ${}^{91}{\rm Y}$ (50 days, 0.59 MeV), ${}^{144}{\rm Ce}$ (170 days, 1.29 MeV), or90 Sr (370 days, 1.13 MeV) in fused aluminosilicate particles. Cerium-144 and90 Sr in fused particles produced more uniform patterns of pulmonary damage than did ${}^{90}{\rm Y}$ or ${}^{91}{\rm Y}$ in fused particles. Fibrosis was more severe in the intermediate than in the peripheral or hilar regions of the lungs of dogs exposed to ${}^{90}{\rm Y}$ in fused particles. That observation was consistent with the relatively greater radiation dose delivered to the peribronchiolar region during the early clearance of ${}^{90}{\rm Y}$. Collagen synthesis and degradation responses in the peripheral and hilar regions of animals exposed to ${}^{91}{\rm Y}$ and in the intermediate area of90 Sr indicated the presence of previously...