Cholesterol, but not cigarette smoke, decreases rabbit carotid artery relaxation

The purpose of this study was to determine the physiologic effects of cigar ette smoke exposure and dietary cholesterol on the availability of nitric o xide in carotid vascular rings. New Zealand white rabbits were placed in an airflow chamber for 3 hr/day over an 8-week period and were exposed to smo ke from 600 cigarettes/per day added to the chamber inflow by a robotic smo ke generator. New Zealand white rabbits, made hypercholesterolemic, and one group fed a normal diet, were similarly placed in the chamber without expo sure to cigarette smoke. In those exposed groups, serum cotinine and choles terol levels were consistantly elevated. After the 8-week period, the carot id arteries were harvested. The vessels were cut into 3-mm rings which were suspended from pressure transducers. The rings were contracted with potass ium chloride (KCI) to determine vessel integrity. One ring from each caroti d was maximally contracted with 1 x 10(-3) molar norepinephrine (NE) while the experimental ring was contracted to 50% of maximum. Relaxation of the r ings was achieved by adding incremental doses of acetylcholine. Our results showed that endothelial dysfunction, as measured by acetylcholine-mediated vasorelaxation, occurs in the rabbit carotid artery when exposed to high d ietary cholesterol. Cigarette exposure alone in this particular vessel did not result in significant alteration in acetylcholine-mediated vasorelaxati on.