Inducible nitric oxide synthase-expressing CD68(+) macrophages were observed in hearts from saline-administered rats after MI (17.75 ± 3.14 in the MI group versus 4.29 ± 4.34 in the MI + 5AZ group, P < 0.05), and Arg1-expressing CD68(+) macrophages were more frequent in 5AZ-administered heart (21.55 ± 8.06 in the MI group versus 67.85 ± 17.37 in the MI + 5AZ group, P < 0.05). Here, ARG1 is linked to myocardial infarction.