Cardiovascular and thermoregulatory responses of unrestrained rats exposed to filtered or unfiltered diesel exhaust

Abstract

Diesel exhaust has been associated with adverse cardiovascular and pulmonary health effects. The relative contributions of the gas phase and particulate components of diesel exhaust are less well understood. We exposed telemetered Wistar–Kyoto rats to air or diesel exhaust that was either filtered (F) or unfiltered [gas-phase plus diesel exhaust particles (DEP)], containing ~1.9 mg/m³ of particulate matter for 5 h/day; 5 days/week for 4 consecutive weeks. Blood pressure (BP), core temperature (T_c), heart rate (HR), and cardiac contractility (CC) estimated by the QA interval were monitored by radiotelemetry during exposure as well as during a 2-week period of recovery. Pulmonary injury and inflammation markers were analysed after 2-day, and 4 weeks of exposure, and 2-week recovery. Exposure to F or DEP was associated with a trend for a reduction in BP during weeks 1, 2 and 4. A reduction in HR in the DEP group was apparent during week 4. Exposure to DEP but not F was associated with significant reduction in CC over weeks 1–4. There was also a slight elevation in T_c during DEP exposure. All telemetry parameters were normal during recovery at night and a 2-week recovery period. Neutrophilic inflammation in bronchoalveolar lavage fluid was evident after 2 days and 4 weeks of exposure to F and DEP. There were no signs of inflammation after 2-week recovery. We found a significant decrease in CC and slight reduction in BP. Exposure to DEP and F is associated with pulmonary inflammation, and mild effects on HR, BP, and T_c but there is a marked effect of DEP on CC.

Keywords::

• Air pollution
• diesel exhaust particles
• gas-phase components
• cardiac contractility
• body temperature
• blood pressure
• heart rate

Acknowledgments

Dr. Ian M. Gilmour (US EPA) provided oversight and assistance for animal exposures. Dr William Linak (US EPA) provided valuable information and explanations on diesel combustion chemistry. We thank Drs. Gary Hatch and Aimen Farraj (U.S. EPA) for their critical review of this manuscript. Disclaimer: The research described in this article has been reviewed by the National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency and approved for publication. Approval does not signify that the contents necessarily reflect the views and the policies of the Agency nor does mention of trade names or commercial products constitute endorsement or recommendation for use.

Declaration of interest

The authors report no conflicts of interest.