Wp. Watkinson et al., Cardiovascular and systemic responses to inhaled pollutants in rodents: Effects of ozone and particulate matter, ENVIR H PER, 109, 2001, pp. 539-546
Striking similarities have been observed in a number of extrapulmonary resp
onses of rodents to seemingly disparate ambient pollutants. These responses
are often characterized by primary decreases in important indices of cardi
ac and thermoregulatory function, along with secondary decreases in associa
ted parameters. For example, when rats are exposed to typical experimental
concentrations of ozone (O-3), they demonstrate robust and consistent decre
ases in heart rate (HR) ranging from 50 to 100 beats per minute, whereas co
re temperature (T-infinity) often falls 1.5-2.5 degreesC. Other related ind
ices, such as metabolism, minute ventilation, blood pressure, and cardiac o
utput, appear to exhibit similar deficits. The magnitudes of the observed d
ecreases may be modulated by changes in experimental conditions and appear
to vary inversely with both ambient temperature and body mass. More recent
studies in which both healthy and compromised rats were exposed to either p
articulate matter or its specific components yielded similar results. The a
gents studied included representative examples of ambient, combustion, and
natural source particles, along with individual or combined exposures to th
eir primary metallic constituents. In addition to the substantial decreases
in HR and T-CO, similar to those seen with the O-3-exposed rats, these ani
mals also displayed numerous adverse changes in electrocardiographic wavefo
rms and cardiac rhythm, frequently resulting in fatal outcomes. Although th
ere is only limited experimental evidence that addresses the underlying mec
hanisms of these responses, there is some indication that they may be relat
ed to stimulation of pulmonary irritant receptors and that they may be at l
east partially mediated via the parasympathetic nervous system.