ENDOTHELIUM-DEPENDENT AND INDEPENDENT RELAXATION OF AORTIC RINGS FROMWATANABE HERITABLE HYPERLIPIDEMIC RABBITS AFTER EXPOSURE TO A FREE-RADICAL GENERATING-SYSTEM

The effects of the xanthine oxidase/hypoxanthine free radical generati ng system on endothelium dependent and independent relaxation were com pared in aortic rings from New Zealand white rabbits and heterozygous Watanabe heritable hyperlipidemic (WHHL) rabbits with mild atheroscler osis. Studies were carried out in young (3 months) and mature (18 mont hs) animals. Plasma cholesterol levels were significantly higher in bo th 3 and 18 month WHHL animals. Endothelium independent relaxation to SNP did not differ between groups. However, the attenuation of relaxat ion to carbachol after xanthine oxidase/hypoxanthine treatment tended to be less in WHHL. This reached significance at 18 but not 3 months. We propose that this could be due to increases in levels of endogenous scavenger enzymes in these WHHL rabbits.