Atheroprotective effects of dietary L-arginine increase with age in cholesterol-fed rabbits

NO has several putative atheroprotective properties but its precursor, L-arginine, and inhibitors of its synthesis have had inconsistent effects on the extent of experimental atherosclerosis in rabbits. The location and character of experimental atherosclerosis differ between immature and mature rabbits; both phenomena have been attributed to changes with age in the NO pathway. We investigated whether the influence of dietary L-arginine on experimental atherosclerosis is also age-related. The frequency of lesions was mapped in the descending thoracic and upper abdominal aorta of immature and mature rabbits fed 1% cholesterol, with or without supplementary L-arginine, for 8 weeks. Consistent with earlier data, the distribution of lesions around the branch points changed with age in control rabbits. The mean frequency of lesions was essentially the same at both ages. L-Arginine supplements had no effect on the distribution of lesions at either age. They significantly reduced the mean frequency of lesions in mature animals but not in immature animals. Thus, the atheroprotective effect of dietary L-arginine in cholesterol-fed rabbits increases with age.