title: Mechanisms of inhaled fine particulate air pollution-induced arterial blood pressure changes.
abstract: BACKGROUND
  Epidemiologic studies suggest a positive association between fine particulate matter and arterial blood pressure, but the results have been inconsistent.
  
  
  OBJECTIVE
  We investigated the effect of ambient particles on systemic hemodynamics during a 5-hr exposure to concentrated ambient air particles (CAPs) or filtered air (FA) in conscious canines.
  
  
  METHODS
  Thirteen dogs were repeatedly exposed via permanent tracheostomy to CAPs (358.1+/-306.7 microg/m3, mean+/-SD) or FA in a crossover protocol (55 CAPs days, 63 FA days). Femoral artery blood pressure was monitored continuously via implanted telemetry devices. We measured baroreceptor reflex sensitivity before and after exposure in a subset of these experiments (n=10 dogs, 19 CAPs days, 20 FA days). In additional experiments, we administered alpha-adrenergic blockade before exposure (n=8 dogs, 16 CAPs days, 15 FA days). Blood pressure, heart rate, rate-pressure product, and baroreceptor reflex sensitivity responses were compared using linear mixed-effects models.
  
  
  RESULTS
  CAPs exposure increased systolic blood pressure (2.7+/-1.0 mmHg, p=0.006), diastolic blood pressure (4.1+/-0.8 mmHg; p<0.001), mean arterial pressure (3.7+/-0.8 mmHg; p<0.001), heart rate (1.6+/-0.5 bpm; p<0.001), and rate-pressure product (539+/-110 bpm x mmHg; p<0.001), and decreased pulse pressure (-1.7+/-0.7 mmHg, p=0.02). These changes were accompanied by a 20+/-6 msec/mmHg (p=0.005) increase in baroreceptor reflex sensitivity after CAPs versus FA. After alpha-adrenergic blockade, responses to CAPs and FA no longer differed significantly.
  
  
  CONCLUSIONS
  Controlled exposure to ambient particles elevates arterial blood pressure. Increased peripheral vascular resistance may mediate these changes, whereas increased baroreceptor reflex sensitivity may compensate for particle-induced alterations in blood pressure.
authors.affiliation: Molecular and Integrative Physiological Sciences Program, Department of Environmental Health, Harvard School of Public Health, and Department of Pathology, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.
authors.forename: Carlo R
authors.initials: CR
authors.lastname: Bartoli
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Wellenius
authors.forename: Edgar A
authors.initials: EA
authors.lastname: Diaz
authors.forename: Joy
authors.initials: J
authors.lastname: Lawrence
authors.forename: Brent A
authors.initials: BA
authors.lastname: Coull
authors.forename: Ichiro
authors.initials: I
authors.lastname: Akiyama
authors.forename: Lani M
authors.initials: LM
authors.lastname: Lee
authors.forename: Kazunori
authors.initials: K
authors.lastname: Okabe
authors.forename: Richard L
authors.initials: RL
authors.lastname: Verrier
authors.forename: John J
authors.initials: JJ
authors.lastname: Godleski