CORONARY VESSEL ALTERATIONS FOLLOWING CHRONIC CARBON-MONOXIDE EXPOSURE IN THE ADULT-RAT

Adult male rats were exposed to 500 ppm CO continuously for 30 days, w hile litter-mate controls remained in room air (AIR). Heart weight-to- body weight ratio and hematocrit were increased significantly. Right v entricle (RV) free wall thickness was increased significantly as was r ight to left heart diameter and average heart diameter. Cross-sectiona l areas of the left ventricle (LV) free wall, interventricular septum (S) and RV midway between the apex and base were increased significant ly. Morphometric analysis of the CO-exposed and AIR hearts revealed no significant differences in the number of small (27-114 mu m) or large r (> 114 mu m) blood vessels in any region; however, there was a trend towards an increased number of the smaller vessels, both arterioles a nd venules, in the CO-exposed rats. The larger arteries in the S and R V were significantly larger in the CO-exposed rats. There was a signif icant overall effect of CO on larger artery diameter across all heart regions, consistent with the appearance of heart radiographs taken. Th ere were no differences in the diameter of the small vessels in any re gion of the heart between the CO exposed and AIR rats. The vessel cros s-sectional area of the larger vessels tended to be increased in all r egions of the heart. The cross-sectional area of the large arteries in the LV was increased significantly. Arterial wad thickness was decrea sed significantly in RV and there was a significant overall effect of CO in decreasing wall thickness and the ratio of wall thickness-to-ves sel luminal diameter in these vessels. No vascular pathology was obser ved. The results of this study suggest changes in coronary vessel arch itecture during chronic CO-induced cardiac hypertrophy and are consist ent with earlier hemodynamic and morphometric studies of CO-exposed he arts.