Increased response of renal perfusion to the antioxidant vitamin C in type 2 diabetes.
BACKGROUND
Reactive oxygen species play a major role in the development of endothelial dysfunction. It is as yet unspecified whether increased oxidative stress contributes to endothelial dysfunction of the renal vasculature in patients with type 2 diabetes.


METHODS
Renal haemodynamics were studied in 20 patients with type 2 diabetes and arterial hypertension (age 62 +/- 5 years) and 20 non-diabetic hypertensive patients at baseline and following infusions of the nitric oxide synthase inhibitor, N(G)-monomethyl-L-arginine (L-NMMA; 4.25 mg/kg); the substrate of nitric oxide synthase, L-arginine (100 mg/kg); and the antioxidant, vitamin C (3 g, co-infused with L-arginine 100 mg/kg).


RESULTS
The response of renal plasma flow (RPF) to L-NMMA (-54 +/- 62 and -45 +/- 42 ml/min/1.73 m(2); P = NS) and L-arginine (+46 +/- 36 and +49 +/- 25 ml/min/1.73 m(2); P = NS) was not different between diabetic and non-diabetic patients. In contrast, vitamin C induced a more pronounced increase in RPF in diabetic than in non-diabetic patients when co-infused with L-arginine (+71+/-47 and +43+/-33 ml/min/1.73 m(2); P<0.05).


CONCLUSIONS
The difference in the response of renal perfusion to an antioxidant suggests increased formation of reactive oxygen species and thereby reduced nitric oxide bioavailability in the renal vasculature of patients with type 2 diabetes.
Delles
Christian
C
Department of Medicine IV/4, University of Erlangen-Nürnberg, Krankenhausstr. 12, D-91054 Erlangen, Germany.
Schneider
Markus P
MP
Oehmer
Sebastian
S
Fleischmann
Ingrid
I
Fleischmann
Erwin F
EF
Schmieder
Roland E
RE
D000368:Aged; D000975:Antioxidants / Q000008:administration & dosage / Q000494:pharmacology*; D001120:Arginine / Q000008:administration & dosage / Q000494:pharmacology; D001205:Ascorbic Acid / Q000008:administration & dosage / Q000494:pharmacology*; D016022:Case-Control Studies; D003924:Diabetes Mellitus, Type 2 / Q000150:complications / Q000503:physiopathology*; D004338:Drug Combinations; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D005260:Female; D006801:Humans; D006973:Hypertension / Q000150:complications / Q000503:physiopathology; D007262:Infusions, Intravenous; D008297:Male; D008875:Middle Aged; D012079:Renal Circulation / Q000187:drug effects*; D019323:omega-N-Methylarginine / Q000008:administration & dosage / Q000494:pharmacology
D000975:Antioxidants; D004338:Drug Combinations; D004791:Enzyme Inhibitors; D019323:omega-N-Methylarginine; D001120:Arginine; D001205:Ascorbic Acid