Observation on early pathological changes in silica exposed rat lung

Objective To study the early pathological changes in silica exposed rat lung.Methods 168 Wistar rats were randomly divided into four groups,i.e.the control group and 3 exposed groups(15,30,and 60 mg/ml respectively)with 42 rats in each group.The silicosis models were established by tracheal instillation.7 rats from each group were sacrificed at 6 definite dates(the 1 st,3 rd,7 th,14 th,21 st,and 28 th day).The lungs were weighed,fixed in formalin,embedded in paraffin,and stained by HE.The pathological changes in lungs were observed under light microscope.Results The organ coefficients of lungs of rat exposed to various doses sacrificed at any dates were higher than that of the control group(P0.05).The dose-response relationship was significant(P0.05).As the exposure time elongated,the surface of rat lungs gradually darkened,the mass enlarged,irregular patches increased,flexibility weakened etc.The HE staining showed that after exposed for 28 days inflammatory reaction associated with diffuse interstitial pulmonary fibrosis were observed mainly.Inflammatory response enhanced as the doses increased,and became more distinctive after exposed for 7~14 days.Interstitial pulmonary fibrosis gradually became more serious as the experimental time prolonged and the doses increased.Conclusions At the early stage of silicosis,inflammatory reaction is obvious.The main manifestations are coagulation of cell infiltration,thickened alveolar septa,and fibrous tissue hyperplasia,finally the normal lung tissue changes.