Inhalation of Simulated Smog Atmospheres Affects Cardiac Function in Mice

The health effects of individual criteria air pollutants have been well investigated. However, little is known about the health effects of air pollutant mixtures that more realistically represent environmental exposures. The present study was designed to evaluate the cardiac effects of inhaled simulated smog atmospheres (SA) generated from the photochemistry of either gasoline and isoprene (SA-G) or isoprene (SA-Is) in mice. Four-month-old female mice were exposed for 4h to filtered air (FA), SA-G, or SA-Is. Immediately and 20h after exposure, cardiac responses were assessed with a Langendorff preparation using a protocol consisting of 20min of global ischemia followed by 2h of reperfusion. Cardiac function was measured by index of left-ventricular developed pressure (LVDP) and cardiac contractility (dP/dt) before ischemia. Pre-ischemic LVDP was lower in mice immediately after SA-Is exposure (52.2 +/- 5.7cm H2O compared to 83.9 +/- 7.4cm H2O after FA exposure; p=0.008) and 20h after SA-G exposure (54.0 +/- 12.7cm H2O compared to 79.3 +/- 7.4cm H2O after FA exposure; p=0.047). Pre-ischemic left ventricular contraction dP/dt(max) was lower in mice immediately after SA-Is exposure (2025 +/- 169cm H2O/sec compared to 3044 +/- 219cm H2O/sec after FA exposure; p<0.05) and 20h after SA-G exposure (1864 +/- 328cm H2O/sec compared to 2650 +/- 258cm H2O/sec after FA exposure; p=0.05). In addition, SA-G reduced the coronary artery flow rate 20h after exposure compared to the FA control. This study demonstrates that acute SA-G and SA-Is exposures decrease LVDP and cardiac contractility in mice, indicating that photochemically-altered atmospheres affect the cardiovascular system.