Effect of particulate matter (PM) and ozone (O 3 ) exposure on heart rate regulation in DBA/2J mice

Abstract

We aimed to determine the effects PM and O3 had on heart rate (HR) and heart rate variability (HRV) in DBA/2J (D2) mice. At 12 months of age, mice with implanted ECG telemeters were exposed to Baltimore PM by aspiration and then O3 by inhalation. In a 3-wk period, mice received weekly aliquots (50 μl) of PM suspended in PBS at incremental concentrations (2, 5, and 10 μg/μl), and then were exposed to O3 (~500 ppb) for 3 hrs after each aspiration. Control mice were repeatedly treated with PBS and exposed to room air. A 3-min ECG was recorded every 15 min for 4 hrs following the exposure sequence. There was a significant (p < 0.05) decline in HR in mice exposed to 2 μg/μl of PM and O3 relative to controls. This same decline in HR was accompanied by significant increases in HRV (SDNN and rMSSD). The changes in HR and HRV were most significant in the 2 μg/μl concentration. Correlation analysis showed that a lower HR occurred at a given level of rMSSD in PM- and O3-exposed mice compared with controls. These data suggest that exposures to Baltimore PM followed by O3 in D2 mice leads to significant declines in HR accompanied by increases in HRV. (Support: AG-21057 and RD-83241701)