The aim of this work was to evaluate the effect of SbIII on cell integrity, expression of profibrotic factors and reactive oxygen species (ROS) in mouse cortical collecting duct cells (M-1 cell line). M-1 cells were incubated with SbIII for 24 h. Cell morphology and RNA expression level (connecting tissue growth factor, CTGF), α-SMOOTH MUSCLE ACTIN (α-SMA) and collagen I were analysed. The total Sb content according to each cell compartment was determined and ROS production was measured. Eighty percent of the total Sb was detected in the extracellular medium. A significant increase in ROS production and CTGF protein expression were observed at 100 μg L-1 SbIII. M-1 cells showed a non-classic epithelial cell shape at 100 μg L-1 and a reduction in the collecting duct-specific marker aquaporin-2. At 100 μg L-1, the number of collagen I-positive cells increased. At 300 μg L-1, a gross cell nuclear rupture was observed. These results demonstrate that an SbIII concentration of 100 μg L-1 is able to promote the induction of CTGF and collagen I along with the induction of ROS, which suggests a cytotoxicity of SbIII in M-1 kidney collecting duct cells.