Unilateral ureteral obstruction (UUO) is a well-established method to study interstitial fibrosis of the kidney. In this study, we investigated the effects of a calcium channel blocker, amlodipine, on UUOinduced renal interstitial fibrosis in mice. UUO significantly increased the fibrotic area in the obstructed kidney, but this change was inhibited by amlodipine (6.7 mg/kg/day in drinking water). mRNA expression of heat shock protein (HSP) 47 and type IV collagen was increased in the kidneys of UUO mice. Amlodipine reduced the expression of both HSP47 and type IV collagen mRNAs. Phosphorylation of c-jun-N-terminal kinase (JNK) was significantly increased by UUO, but the change was inhibited by amlodipine. Collectively, these results suggest that amlodipine may inhibit the expression of HSP47 and type IV collagen by reducing phosphorylation of JNK and ameliorating the renal interstitial fibrosis induced by UUO. (C) 2016 Elsevier B.V. All rights reserved.