[A comparative morphological and enzyme-histochemical study of experimental pneumoconiosis and experimental allergic-hyperergic pulmonary granuloma (author's transl)].

Six endotracheal applications of 15 milligrams of cadmium sulfide (CdS) given to rats at weekly intervals induce pneumoconiosis with massive adhesions. The same quantities of lead sulfide (PbS) given under the same conditions have much less effect, causing only the formation of fairly small fibrous nodules. The tissue reactions to CdS and PbS were studied morphologically (light and electron microscope) and enzyme-histochemically. The results were compared with those observed in experimental anthracosilicosis in rats and with those seen in allergic-hyperergic reactions of the lung in guinea pigs (induced by several applications of the complete Freund adjuvans). A considerable increase in macrophages in the alveoli and interstices of the lungs with increased activity of acid phosphatase and oxydoreductases had occurred in every animal. None showed primary damage to type 2 pneumocytes. The results indicate that the two toxic agents differ in their capacity to induce fibrosis not because they interfere to a different degree with the clearing function of the lung or surfactant production, but because they differ in their capacity to stimulate fibroblast formation.