Contrast-induced nephropathy represents the third cause of hospital-acquired 
acute renal failure. This study investigated the effects of low- vs iso-osmolar 
contrast medium (CM) exposure on NADPH-dependent reactive oxygen species (ROS) 
generation by tubular cells. X-ray attenuation of iohexol, iopamidol, and 
iodixanol was assessed at equimolar iodine concentrations and their effects on 
human renal proximal tubular cells (PTCs) were evaluated with equally 
attenuating solutions of each CM. Cytotoxicity, apoptosis, and necrosis were 
investigated by trypan blue exclusion, MTT assay, and annexin V/propidium iodide 
assay, respectively. ROS production was assessed by DCF assay, NADPH oxidase 
activity by the lucigenin-enhanced chemiluminescence method, and Nox4 expression 
by immunoblot. Yielding the same X-ray attenuation, CM cytotoxicity was assessed 
in PTCs at equimolar iodine concentrations. More necrosis was present after 
incubation with iohexol and iopamidol than after incubation with equal 
concentrations of iodixanol. Iohexol and iodixanol at low iodine concentrations 
induced less cytotoxicity than iopamidol. Moreover, both iohexol and iopamidol 
induced more apoptosis than iodixanol, with a dose-dependent effect. ROS 
generation was significantly higher with iopamidol and iohexol compared to 
iodixanol. NADPH oxidase activity and Nox4 protein expression significantly 
increased after exposure to iopamidol and iohexol, with a dose-dependent effect, 
compared with iodixanol. CM-induced Nox4 expression and activity depended upon 
Src activation. In conclusion, at angiographic concentrations, iodixanol induces 
fewer cytotoxic effects on cultured tubular cells than iohexol and iopamidol 
along with a lower induction of Nox4-dependent ROS generation. This enzyme may, 
thus, represent a potential therapeutic target to prevent iodinated CM-related 
oxidative stress.