Atypical quartz dust-induced pneumoconiosis in SPF rats. Aspects of the role of the lymphatic system in the pathogenesis of silicosis.

Experimental exposure to quartz dust for 100 days (= 700 h) induces in SPF rats histologic changes of the lungs, which have such striking similarities with human cases of pulmonary alveolar proteinosis that they may represent an animal model of human disease. Conventional stock rats, the standard model of experimental silicosis research, react upon the same dosage of quartz dust by the formation or an increase in size of perivascular lymphatic sheaths, in which epitheloid cell granulomas can arise. In SPF rats such granulomas can only be developed in the sparse pre-existent lymphatic tissue, mostly in hilar lymph nodes. The reaction of SPF rats opens an interesting aspect on the significance of the phenomenon of lymphatic "drainage," as comparable reactions are only known in conventional rats following extreme dosage and in human pathology as so-called acute silicoproteinosis.