Hypoxia-induced leptin expression in HCASMCs is mediated by reactive oxygen species (ROS). (A and B) ROS assay, using a fluorescence microscope, indicated that hypoxia for 1 hour increased ROS production similarly to that of the exogenous addition of Dp44mT or AngII. Treatment with NAC (500 μM) or AngII type 1 receptor blocker (ARB; losartan 100 nM) 1 hour before hypoxia significantly blocked the induction. *P < 0.01 vs. normoxia control. #P < 0.01 vs. 1 h (n = 3).