“…As the concentrations of As(V) and MMA in female rats were higher than in males, the differences in arsenic distribution may be the cause of the differences in liver response. Although it is not clear why As(V) and MMA concentrations were higher in female rats than in males, it might be due to sex differences in arsenic metabolism, such as higher methylation capacity, which metabolizes As(III) to MMA, and lower purine nucleoside phosphorylase (PNP) activity, which reduces As(V) to As(III), in female rats than in males 26 .…”