Tetrahydrobiopterin, L-arginine and vitamin C actsynergistically to decrease oxidative stress, increase nitricoxide and improve blood flow after induction of hindlimbischemia in the rat

Nitric oxide (NO) derived from endothelial nitric oxide synthase (eNOS) is a potent vasodilator and signaling molecule that plays an essential role in vascular remodeling of collateral arteries and perfusion recovery in response to hindlimb ischemia. In ischemic conditions, decreased NO bioavailability was observed because of increased oxidative stress, decreased l-arginine and tetrahy-drobiopterin. This study tested the hypothesis that dietary cosupplementation with tetrahydrobiopterin (BH4), l-arginine, and vitamin C acts synergistically to decrease oxidative stress, increase nitric oxide and improve blood flow in response to acute hindlimb ischemia. Rats were fed normal chow, chow supplemented with BH4 or l-arginine (alone or in combination) or chow supplemented with BH4 + l-arginine + vitamin C for 1 wk before induction of unilateral hindlimb ischemia. Cosupplementation with BH4 + l-arginine resulted in greater eNOS expression, Ca²⁺-dependent NOS activity and NO concentration in gastrocnemius from the is-chemic hindlimb, as well as greater recovery of foot perfusion and more collateral artery enlargement than did rats receiving either agent separately. The addition of vitamin C to the BH4 + l-arginine regimen did further increase these dependent variables, although only the increase in eNOS expression reached statistical significances. In addition, rats given all three supplements demonstrated significantly less Ca²⁺-independent activity, less nitrotyrosine accumulation, greater glutathione:glutathione disulfide (GSH:GSSG) ratio and less gastrocnemius muscle necrosis, on both macroscopic and microscopic levels. In conclusion, cosupplementation with BH4 + l-arginine + vitamin C significantly increased vascular perfusion after hindlimb ischemia by increasing eNOS activity and reducing oxidative stress and tissue necrosis. Oral cosupplementation of l-arginine, BH4 and vitamin C holds promise as a biological therapy to induce collateral artery enlargement.