RESUMEN
OBJECTIVE@#To investigate ultrastructural changes in pulmonary tissue of a rat model of pulmonary fibrosis following treatment with compound Carapax trionycis (C. trionycis; Biejia in Chinese) formula.@*METHODS@#Sixty male Sprague-Dawley rats were randomly divided into four groups (n=15): compound C. trionycis formula high-, middle-, and low-dose groups as well as model group. Pulmonary fibrosis was induced by bleomycin. Five rats from each group were sacrificed on day 7, 14 and 28 of the drug treatment, respectively. The pulmonary tissue was harvested followed by hematoxylin-eosin staining and subsequent transmission electron microscopy. The Szapiel's method was used to assess the degree of alveolitis and pulmonary fibrosis.@*RESULTS@#Compared with the model group, the compound C. trionycis formula groups had slighter pulmonary alveolitis after the 7-day treatment and also had alleviated alveolar inflammation and pulmonary fibrosis after the 14-day treatment. After the 28-day treatment, the compound C. trionycis formula groups showed deposition of a small amount of fibrous tissue and lesions occupying less than 21% of the whole lung area, while the model group showed focal or diffuse fibrous deposition, narrow alveolar cavity, disordered lung structure, and lesions in larger than 51% of the whole lung area.@*CONCLUSIONS@#The compound C. trionycis formula can inhibit the proliferation of collagen fibers and resist pulmonary fibrosis.