Further, our results extend previous studies showing a reduction of spermine content in the kidneys of UUO and IRI mice,[29, 32] as well as decreased renal tubular epithelial cellular levels of spermine upon TGF‐β1 exposure.[32] In vivo, we also found that the levels of spermidine were significantly increased in the kidneys of both fibrosis models, while putrescine was elevated only in UUO kidneys. This evidence concerns the gene TGFB1 and fibrosis.