DIETARY-CHOLESTEROL INDUCES TRANSIENT CHANGES IN PLASMA NITRATE LEVELS IN RABBITS THAT ARE CORRELATED TO MICROCIRCULATORY CHANGES

Dietary treatment of rabbits with 1% cholesterol resulted in a transie nt rise in their plasma nitrate levels. After 3 weeks of treatment the nitrate levels were about 50% higher than those of the controls (p < 0.005). After 10 weeks of treatment the nitrate levels were similar to those at the start of the study. In accordance with previous work (Xi u et al, J. Clin. Invest., 1994, 93, 2732-2737), the cholesterol treat ment led to a decreased blood flow velocity in arterioli of the third order in the conjunctiva, and a decreased diameter of these arterioli. There was a significant correlation between plasma nitrate levels and the two microcirculatory variables (p < 0.0001). Nitrate is the major metabolic end product of nitric oxide (NO), and plasma nitrate levels may be used as an index of the endogenous formation of NO. The presen t results suggest that dietary cholesterol induces a transient increas e in the synthesis of NO. Such an increased synthesis may compensate f or part of a cholesterol-induced degradation of NO. (C) 1996 Academic Press Inc.