To determine whether the TGF-β1/Smad2/3 signaling pathway is an essential intermediary in KCa3.1 mediated diabetic nephropathy, we examined the effects of KCa3.1 on the expression of TGF-β1 in kidneys of mice with established diabetic nephropathy using real-time PCR and immunohistochemical staining. The gene discussed is KCNN4; the disease is diabetic kidney disease.