SLC7A2 and pulmonary fibrosis: This is based on the following: 1) CAT2 is upregulated in bleomycin-induced pulmonary fibrosis [19] and 2) arginase metabolizes arginine to ornithine, which can be further metabolized by ornithine aminotransferase to proline, an amino acid that is often the rate-limiting substrate for collagen synthesis.