Adverse cardiovascular effects with acute particulate matter and ozone exposures: interstrain variation in mice.
OBJECTIVE
Increased ambient particulate matter (PM) levels are associated with cardiovascular morbidity and mortality, as shown by numerous epidemiology studies. Few studies have investigated the role of copollutants, such as ozone, in this association. Furthermore, the mechanisms by which PM affects cardiac function remain uncertain. We hypothesized that PM and O(3) induce adverse cardiovascular effects in mice and that these effects are strain dependent.


METHODS
After implanting radiotelemeters to measure heart rate (HR) and HR variability (HRV) parameters, we exposed C57Bl/6J (B6), C3H/HeJ (HeJ), and C3H/HeOuJ (OuJ) inbred mouse strains to three different daily exposures of filtered air (FA), carbon black particles (CB), or O(3) and CB sequentially [O(3)CB; for CB, 536 +/- 24 microg/m(3); for O(3), 584 +/- 35 ppb (mean +/- SE)].


RESULTS
We observed significant changes in HR and HRV in all strains due to O(3)CB exposure, but not due to sequential FA and CB exposure (FACB). The data suggest that primarily acute HR and HRV effects occur during O(3)CB exposure, especially in HeJ and OuJ mice. For example, HeJ and OuJ mice demonstrated dramatic increases in HRV parameters associated with marked brady-cardia during O(3)CB exposure. In contrast, depressed HR responses occurred in B6 mice without detectable changes in HRV parameters.


CONCLUSIONS
These findings demonstrate that important interstrain differences exist with respect to PM- and O(3)-induced cardiac effects. This interstrain variation suggests that genetic factors may modulate HR regulation in response to and recuperation from acute copollutant exposures.
Hamade
Ali K
AK
Department of Environmental Health Sciences, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland 21205, USA.
Rabold
Richard
R
Tankersley
Clarke G
CG
D000818:Animals; D002940:Circadian Rhythm; D004781:Environmental Exposure; D006339:Heart Rate / Q000187:drug effects*; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008815:Mice, Inbred Strains; D010126:Ozone / Q000633:toxicity*; D052638:Particulate Matter / Q000633:toxicity*; D053260:Soot / Q000633:toxicity*; D013686:Telemetry
D052638:Particulate Matter; D053260:Soot; D010126:Ozone