title: Dobutamine "stress" test and latent cardiac susceptibility to inhaled diesel exhaust in normal and hypertensive rats.
abstract: BACKGROUND
  Exercise "stress" testing is a screening tool used to determine the amount of stress for which the heart can compensate before developing abnormal rhythm or ischemia, particularly in susceptible persons. Although this approach has been used to assess risk in humans exposed to air pollution, it has never been applied to rodent studies.
  
  
  OBJECTIVE
  We hypothesized that a single exposure to diesel exhaust (DE) would increase the risk of adverse cardiac events such as arrhythmia and myocardial ischemia in rats undergoing a dobutamine challenge test, which can be used to mimic exercise-like stress.
  
  
  METHODS
  Wistar-Kyoto normotensive (WKY) and spontaneously hypertensive (SH) rats implanted with radiotelemeters and a chronic intravenous catheter were whole-body exposed to 150 μg/m3 DE for 4 hr. Increasing doses of dobutamine, a β1-adrenergic agonist, were administered to conscious unrestrained rats 24 hr later to elicit the cardiac response observed during exercise while heart rate (HR) and electrocardiogram (ECG) were monitored.
  
  
  RESULTS
  A single exposure to DE potentiated the HR response of WKY and SH rats during dobutamine challenge and prevented HR recovery at rest. During peak challenge, DE-exposed SH rats had lower overall HR variability when compared with controls, in addition to transient ST depression. All DE-exposed animals also had increased arrhythmias.
  
  
  CONCLUSIONS
  These results are the first evidence that rats exhibit stress-induced cardiac dysrhythmia and ischemia sensitivity comparable to humans after a single exposure to a toxic air pollutant, particularly when in the presence of underlying cardiovascular disease. Thus, exposure to low concentrations of air pollution can impair the heart's ability to respond to stress and increase the risk of subsequent triggered dysfunction.
authors.affiliation: Environmental Public Health Division, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA. hazari.mehdi@epa.gov
authors.forename: Mehdi S
authors.initials: MS
authors.lastname: Hazari
authors.forename: Justin
authors.initials: J
authors.lastname: Callaway
authors.forename: Darrell W
authors.initials: DW
authors.lastname: Winsett
authors.forename: Christina
authors.initials: C
authors.lastname: Lamb
authors.forename: Najwa
authors.initials: N
authors.lastname: Haykal-Coates
authors.forename: Q Todd
authors.initials: QT
authors.lastname: Krantz
authors.forename: Charly
authors.initials: C
authors.lastname: King
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Costa
authors.forename: Aimen K
authors.initials: AK
authors.lastname: Farraj
mesh_terms: D000818:Animals; D004280:Dobutamine / Q000008:administration & dosage*; D004562:Electrocardiography; D005080:Exercise Test; D006321:Heart / Q000502:physiology* / Q000503:physiopathology; D006339:Heart Rate; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D012119:Respiration; D001335:Vehicle Emissions / Q000633:toxicity*
chemical_list: D001335:Vehicle Emissions; D004280:Dobutamine