Background and objective Pulmonary fibrosis is a common pathological phenomenon in lung cancer patients after chemotherapy or radiotherapy. It is also a key hindrance to the transport of drugs to lung tissue. Peptide transporters have become a target of the rational design of peptides and peptide drugs. The aim of this study is to investigates the expression of peptide transporter 2 (PEPT2) mRNA in the lungs of rats with bleomycin (BLM)-induced pulmonary fibrosis. Methods Fifty healthy adult Sprague-Dawley rats were randomly divided into five groups. One group was untreated (control), the second group was injected with normal saline solution (NS), and the three remaining groups were treated with a single dose of bleomycin to induce pulmonary fibrosis (BLM). Rats from the NS group were killed by exsanguination on day 14. Rats from the BLM group were killed by exsanguination on days 7, 14, and 28. The lung samples were observed under light microscopy and the hydroxyproline concentration was determined. The expression levels of PEPT2 mRNA were measured by RT-PCR. Results The morphological study showed that collagenous fiber proliferated in the lungs of rats injected with BLM, indicating pulmonary fibrosis. This proliferation was apparent at 14 d post-injection and especially at 28 d post-injection. Hydroxyproline levels increased seven days post-injection compared with the control group and NS group, but there was no significant statistical difference (P>0.05). Hydroxyproline levels significantly increased (P<0.05) 14 d and 28 d post-infection. The change in the lung tissue pathology coincided with the change in hydroxyproline levels. There were no significant changes of pulmonary PEPT2 mRNA expression levels among the different groups (P>0.05). Conclusion PEPT2 is a potential peptide drug target in the treatment of pulmonary fibrosis, although there were no significant changes of PEPT2 mRNA expression in the lungs of rats with bleomycin-induced pulmonary fibrosis.