['Few studies have addressed the effect of vasodilatory stimuli on the intrarenal arterial system in type 2 diabetes mellitus (DM), and factors affecting its responsiveness.', 'One hundred twenty-four patients with type 2 DM without renal failure were enrolled, and 25 subjects served as controls. Using duplex Doppler sonography, resistive indices (RI) of interlobar arteries were measured before and after sublingual nitroglycerine (NTG) (0.3 mg) spray over a 10-min period.', 'Per cent changes in RI (%DeltaRI) in the DM group were significantly less than in controls (P<0.05), as was the area over the %DeltaRI-time curve (AOC-%DeltaRI, total responsiveness to nitroglycerine) (P<0.05). In the DM group, significant negative correlations were found between AOC-%DeltaRI and age (r=-0.492, P<0.0001). AOC-%DeltaRI in DM patients with proteinuria was significantly lower than without it (P<0.003). AOC-%DeltaRI in smokers was also significantly lower than in nonsmokers (P<0.05). By multiple regression analysis of the DM group, AOC-%DeltaRI was found to be significantly and independently affected by age (beta=-0.394), smoking (beta=-0.211), and the presence of proteinuria (beta=-0.270; R(2)=0.354, P<0.0001).'] Do smoking and proteinuria impair vasodilatory response of intrarenal arteries to nitroglycerine in patients with type 2 diabetes mellitus?