Cardiac dysfunction subsequent to chronic ozone exposure in rats

A number of advancements have been made toward identifying the risk factors associated with cardiovascular disease (CVD) and have resulted in a decline in mortality. However, many patients with cardiac disease show no established previous risk. Thus, it appears that other unknown factors contribute to the pathophysiology of CVD. Out of 350,000 sudden cardiac deaths each year in the United States, 60,000 deaths have been linked to air pollution, suggesting a detrimental role of environmental pollutants in the development of CVD. This study tested the hypothesis that chronic ozone (O(3)) exposure diminishes myocardial function in healthy population. Male Sprague-Dawley rats were exposed 8 h/day for 28 and 56 days to filtered air or 0.8 ppm O(3). In vivo cardiac function was assessed by measuring LVDP, +dP/dt, -dP/dt, and LVEDP 24 h after termination of the O(3) exposure. Compared to rats exposed to filtered air, LVDP, +dP/dt, and -dP/dt were significantly decreased, and LVEDP was significantly increased in O(3) exposed animals. This attenuation of cardiac function was associated with increased myocardial TNF-alpha levels and lipid peroxidation as well as decreased myocardial activities of superoxidase dismutase and interleukin-10 levels. These novel findings suggest myocardial dysfunction subsequent to chronic O(3) exposure in normal adult rats may be associated with a decrease in antioxidant reserve and with an increased production of inflammatory mediators.