Role of Nitric Oxide in Restenosis After Experimental Balloon Angioplasty in the Hypercholesterolemic Rabbit: Effects on Neointimal Hyperplasia and Vascular Remodeling

Abstract OBJECTIVES The purpose of this study was to assess the effects of L-arginine and N G -nitro-L-arginine methyl ester (L-NAME) on neointimal hyperplasia and vascular remodeling after balloon angioplasty in the hypercholesterolemic rabbit. BACKGROUND Restenosis after balloon angioplasty is a consequence of both neointimal hyperplasia and vessel remodeling. Nitric oxide inhibits neointimal hyperplasia, but its effect on vessel remodeling is unknown. METHODS Six weeks after induction of bilateral iliac atherosclerosis, 48 rabbits underwent successful angioplasty in 75 vessels. Eight rabbits (acute group) were sacrificed immediately after angioplasty. The remaining animals received either placebo (chronic control group), or a diet supplemented with either L-arginine (1.5 g/kg/day), or L-NAME (15 mg/kg/day) for 4 weeks after angioplasty. RESULTS The intimal area was significantly greater in the chronic control group compared to the acute group (2.60 ± 1.03 mm 2 vs. 1.35 ± 0.62 mm 2 ). This increase in intimal area was lower in the L-arginine group (1.79 ± 0.61 mm 2 ), and greater in the L-NAME group (3.23 ± 0.92 mm 2 ). The area circumscribed by the internal elastic lamina (IEL) increased significantly in the control group compared to the acute group (from 2.52 ± 0.66 to 3.33 ± 0.85 mm 2 ); a more marked increase occurred in the L-NAME group (3.90 ± 0.85 mm 2 ). By contrast, IEL area was unchanged in the L-arginine group (2.41 ± 0.62 mm 2 ). As a result, there was no significant difference in lumen area after 4 weeks in the chronic groups (control: 0.74 ± 0.38 mm 2 ; L-arginine: 0.50 ± 0.43 mm 2 ; L-NAME: 0.48 ± 0.42 mm 2 ). CONCLUSIONS Our results demonstrate that L-arginine inhibits whereas L-NAME stimulates neointimal hyperplasia after experimental balloon angioplasty in the hypercholesterolemic rabbit. However, the lack of vessel enlargement in the L-arginine group resulted in a similar final lumen size in the L-NAME and L-arginine groups.