Up to 36 subjects with type 2 diabetes and more than 150 mg of proteinuria who are on stable doses of ACE inhibitors or angiotensin receptor blockers (ARBs) and up to 18 healthy volunteers will be enrolled in this study. Subjects with type 2 diabetes will be asked to stop their ACE inhibitor or ARB medications for 10 days. Between 7 to 10 days after stopping these medications renal blood flow (RBF) will be measured using contrast enhanced ultrasound (CEU) and urine protein will be measured as well for comparison to baseline. Subjects' ACE inhibitors or ARB will be restarted and RBF measurement using CEU and measurement of urine protein excretion will be repeated after 7 days. For comparison, RBF will be measured by CEU in up to 18 healthy volunteers. They will then be started on Lisinopril 10 mg orally once a day for 7 days. On day 7 RBF measurement will be repeated to assess the effect of ACE inhibitors on RBF in healthy individuals as compared to those with diabetic nephropathy.