ARG1 and endothelial dysfunction: 2001). The two arginase isoforms, ARG1 and ARG2, have similar kinetic properties, but are encoded by separate genes. Both ARG1 and ARG2 proteins were demonstrated in endothelium (for a review, see Pernow and Jung (2013)) and implicated in endothelial dysfunction. Increased Arg1 expression is associated with endothelial dysfunction in diabetic patients (Bagi et al. 2013; Beleznai et al. 2011) and mice (Romero et al. 2012; Toque et al. 2013a).