Effects of dietary L-arginine on structure and function of flow-restricted vein grafts

Purpose: Experiments were designed to determine effects of dietary supplementation with L-arginine on structure and function of flow-restricted vein grafts. Methods: Saphenous veins were placed as bilateral interposition grafts in femoral arteries of two groups of adult male mongrel dogs; one group was maintained on a normal diet (control), the other group supplemented with L-arginine (200 mg/kg per day) beginning 1 week before surgery. In each dog, flow was reduced by 50% in one graft by placing an adjustable clamp on the artery distal to the distal anastomosis. Plasma amino acids and oxidized products of nitric oxide (NO_x) were measured before and after L-arginine feeding. At postoperative week 4, grafts were removed and prepared for organ chamber studies to determine functions of the endothelium or smooth muscle and for histology. Results: Plasma L-arginine increased within 3 hours after feeding and increased from 141 ± 8 nmol/mL to 169 ± 11 nmol/mL (n = 6) after 5 weeks of supplementation. Plasma ornithine and citrulline paralleled arginine, whereas circulating NO_x was unchanged. Maximal contractions to 60 mmol/L KCl were reduced in grafts from L-arginine-fed dogs. Endothelium-dependent relaxations to the calcium ionophore A23187 and relaxations of the smooth muscle NO were reduced in grafts from L-arginine-fed dogs. Neointimal hyperplasia was increased in grafts with reduced flow and not affected by arginine feeding. Conclusions: Dietary supplementation with L-arginine did not increase plasma NO in dogs with peripheral vein grafts or increase endothelium-dependent relaxations in control or flow-restricted grafts. Therefore, dietary supplementation with L-arginine may not improve long-term functions of flow-restricted peripheral bypass grafts. (J Vasc Surg 2001;33:829-39).