Objective:Pulmonary fibrosis is a common pathological phenomena in lung cancer patients after chemotherapy or radiotherapy, which is a key factor hindering to transport ion of high concentrated drug to the lung tissue, peptide trans-porter has become targets of the rational design of peptides and peptide drug. The purpose of the study is to investigate the expression of PEPT2 mRNA in the lung of rats with bleomycin (BLM)-induced pulmonary fibrosis. Methods:Fifty healthy adult Spragne-Dawley rats were randomized into five groups, the rats in BLM 7d, 14d and 28d groups were treated with a single instil ation of 5 mg/kg of BLM, to induced pulmonary fibrosis models. On days 7, 14 and 28, the animals were kil ed by exsan-guination respectively. Normal saline (NS) group were treated by NS, on days 14, the animals were kil ed by exsanguinations. Control group were untreated. The lung samples were processed for light microscopy and determined the hydroxyproline (HYP) concentration. The expression of PEPT2 mRNA were measured by RT-PCR. PEPT2 cDNA fragments were tested by dideoxy chain termination. Results:Compared with control and NS group, HYP levels increased on day 7 of BLM group, but there was no statistical significant dif erence (P>0.05). HYP levels markedly increased on days 14 and 28 of BLM group, there was statistical significant dif erence (P0.05). Conclusion:The pulmonary fibrosis models of SD rats can be induced by a single instil ation of 5 mg/kg of bleomycin on 28d. There were no significant changes of PEPT2 mRNA expression in the lung of rats with bleomycin-induced pulmonary fibrosis.