Three groups of four beagle dogs inhaled a <tex-math>${}^{144}{\rm Ce}$</tex-math> labeled fused clay aerosol; two additional dogs per group, exposed to a stable cerium-labeled fused clay aerosol, were used as controls. At monthly intervals, one diaphragmatic lobe of each of two dogs exposed to <tex-math>${}^{144}{\rm Ce}$</tex-math> and one control animal from each group was lavaged with isotonic saline. The recovered lavage solutions were centrifuged to isolate lung cells (mostly macrophages) and surfactant for lipid analyses. The groups were sacrificed at 2, 4, and 6 mo after exposure, when the lungs of the dogs exposed to <tex-math>${}^{144}{\rm Ce}$</tex-math> had average cumulative radiation doses of 23, 36 and 59 krad, respectively. Chronic irradiation of the lung resulted in a progressive radiation pneumonitis which was assessed clinically and pathologically at various intervals. At sacrifice, the lungs were analyzed for <tex-math>${}^{144}{\rm Ce}$</tex-math> and the right apical and diaphragmatic lobes were minced and lyophilized and the lipids were extracted. Total lipids from all lung samples were determined gravimetrically and individual compounds were identified, isolated and quantitated. The quantities of lipid in lung tissue, in pulmonary cells and in surfactant increased as a function of time and radiation dose. Neutral lipids (sterol esters and triglycerides) accounted for most of the increase.

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