ABSTRACT
<p><b>AIM</b>To observe the expression of a-smooth muscle actin(a-SMA) in primary cultural fibroblasts of rats.</p><p><b>METHODS</b>12 female Wistar rats were randomly assigned into two groups, the normal group and the model group. The model group was filled with bleomycin A2 (5 mg/kg) once into the trachea. The normal group was filled with equal saline into the trachea. The rats were sacrificed under drugged state at 28 days of feeding, then Hematoxylin-Eosin staining and electron microscopy were used to evaluate the foundation of the model. The isolated fibroblasts from the rats were cultured in vitro. Flow cytometry was used in the test to observe the expression of alpha-SMA in fibroblast in vitro in rats.</p><p><b>RESULTS</b>The formation of fibroblast foci was observed in the model group by optical microscope. The ultrastructure in pulmonary tissue of the model group rats were changed and proliferated myofibroblasts with filaments were found in the alveolar septa by electron microscopy. The expression of alpha-SMA was positive in the normal and model group. There was no difference between the two groups in the rates of positive cells (P > 0.05).</p><p><b>CONCLUSION</b>Both the normal and model groups had the phenotype conversion in lung fibroblasts in vitro.</p>