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Irreversible pulmonary changes after dust overloading of lungs in rats


Journal of Aerosol Medicine 3 (1990), Nr.1, S.68-69
ISSN: 0894-2684
Particle Lung Interactions <1990, Rochester/N.Y.>
Fraunhofer ITA ( ITEM) ()
Inhalation; inhalation experiment; Inhalationsversuch; lung; lung clearance; lung overloading; lunge; lungenclearance; lungenüberladung; rat; Ratte; toner

The objective of this study was to investigate whether the effects if lung overloading are reversible upon cessation of a subchronic exposure to test toner. Female SPF F-344 rats were exposed 6hrs/day 5 days/week for 3 months to test toner at 0,10 and 40 mg/m3. Alveolar clearance of an 85 Sr-polystyrene tracer aerosol, and retention of the toner in lungs and lymph nodes were evaluated at the end of exposure and subsequently up to 15 months later. The retained quantity of test toner in the lungs at the end of exposure was 0.4 and 3 mg for the low and high exposure groups, respectively. 15 months later the corresponding values were 0.12 and 2.65 mg in the lungs. The alveolar clearance of the tracer aerosol was slightly retarded at the low and substantially impaired at the high exposure level. At the low exposure level, there was some recovery in the slowed clearance behaviour sixmonths post exposure. In contrast, at the high exposure level, there was no indication of a reversal of the im paired clearance. A kinetic model was developed to describe retention of test toner and of labelled particles in the lungs and in the lymph nodes. The assumptions are the following: The lung is divided into two compartments, which contain mobile and immobile macrophages, respectively. Macrophages with a particle burden above a critical volume are immobilized. By chemotaxis the nearest macrophages can migrate into the compartment of immobile macrophages. With this model all experimental data can be fitted well by only 5 parameters.