These results are consistent with our previous report that the inhibitory effects of PetA on fibronectin production in rat kidney tubular epithelial cells (NRK52E) under the stimulation of TGF‐β1.26 Therefore, the inhibition of renal fibrosis by petA is mediated at least partly by the suppression of the TGF‐β1/Smad axis in the obstructed kidneys. Here, TGFB1 is linked to renal fibrosis.