Chronic carbon monoxide exposure in young rats alters coronary vessel growth.

The goal of this study was to determine whether chronic monoxide exposure in the developing heart produces long-lasting coronary vasculature alterations. One-day-old male rat pups were exposed to 500 ppm CO continuously for 30 d, while littermate controls remained in room air (AIR). At 61 and 110 d of age hearts were removed, perfusion fixed, x-rayed, and processed for analysis of coronary vessel architecture. Body weight (BW) and heart weight (HW) increased with age; the ratio of HW/BW decreased. There were no differences in HW and ventricular dimensions at either age due to prior CO exposure. Morphometric analysis of the fixed hearts from CO-exposed and AIR rats revealed no significant individual group differences in the number of small (27-114 microns) or larger (> 114 microns) vessels in any heart region. The septum (S) in CO rats was an exception: There were more small veins at 61 d of age and more larger veins at 110 d of age. There was a significant increase in the number of small arteries at both ages in the CO rats across all heart regions, and in the smaller veins at 61 d of age. The large vessels in the S at 61 d of age had a significantly greater diameter in CO compared to AIR rats. This was also true for the large arteries in the S and right ventricle (RV) of the 110-d-old rats. Taking all heart regions together, the large arteries in CO rats were larger than in AIR rats. Previous CO exposure significantly increased large artery and total cross-sectional area in the S and RV at 61 d of age, and in RV at 110 d of age. Total cross-sectional area of veins in the S was also increased. Taking all heart regions together, CO significantly increased small artery cross-sectional area at 61 d of age, and small, large, and total artery cross-sectional area at 110 d of age. With one exception (small veins, 110 d of age), there was no effect of CO on vein cross-sectional area. These changes resulted in the percentage of total cross-sectional area contributed by the larger vessels being increased. Pathological examination showed nothing abnormal. The results suggest profound and persistent changes in coronary vessel architecture following chronic neonatal CO exposure.