Diabetes is associated with impaired vascular reactivity and development of diabetic nephropathy. In a rat model of streptozotocin-induced diabetic nephropathy the effects of systemic nitric oxide (NO) synthesis inhibition on intrarenal diffusion and oxygenation were determined by magnetic resonance diffusion tensor imaging (DTI) and blood oxygen level dependency imaging (BOLD), respectively. Eight weeks after diabetes induction 21 rats (n=7 per group) - untreated controls, diabetes (DM), diabetes with uninephrectomy (DM UNX) - were examined. DTI and BOLD sequences were acquired before and after NO synthesis inhibition with N-nitro-L-arginine-methyl-ester (L-NAME). In the same rats mean arterial pressure (MAP) and vascular conductance were determined, with and without the influence of L-NAME. In control animals, NO synthesis inhibition was associated with a significant increase of MAP of 33.8±4.3 mmHg (p<0.001) and a decrease of vascular conductance of -17.8±2.0 µl/(min*100mmHg) (p<0.001). These changes were attenuated in both diabetes groups with no significant difference between pre and post L-NAME measurements in DM UNX animals. Similarly, L-NAME challenge induced a significant reduction of renal T2* at MRI in control animals, indicating reduced renal oxygenation after L-NAME injection compared to baseline. DM UNX animals did not show a significant T2*-reduction after NO synthesis inhibition in the renal cortex and attenuated T2*-reduction in the outer medulla. MRI parameters of tissue diffusion were not affected by L-NAME in all groups. In conclusion, BOLD imaging proved valuable to non-invasively measure renal vascular reactivity upon NO synthesis inhibition in control animals and to detect impaired vascular reactivity in animals with diabetic nephropathy.