The NOS inhibitor N(ω)-nitro-l-arginine methyl ester (L-NAME), administered prior to anaemia, prevented the anaemia-induced increases in heart rate (HR), end-diastolic volume (EDV), stroke volume (SV) and cardiac output (CO) and the same response was seen in eNOS−/− mice (Fig. 2). Here, NOS2 is linked to anemia (phenotype).