Effects of Concentrated Ambient Particles on Heart Rate and Blood Pressure in Pulmonary Hypertensive Rats. (Research Articles)

By Cheng, Tsun-Jen; Hwang, Jing-Shiang et al. | Environmental Health Perspectives, February 2003 | Go to article overview

Effects of Concentrated Ambient Particles on Heart Rate and Blood Pressure in Pulmonary Hypertensive Rats. (Research Articles)


Cheng, Tsun-Jen, Hwang, Jing-Shiang, Wang, Peng-Yau, Tsai, Chia-Fang, Chen, Chun-Yen, Lin, Sheng-Hsiang, Chan, Chang-Chuan, Environmental Health Perspectives


Epidemiologic studies have shown that increased concentrations of ambient particles are associated with cardiovascular morbidity and mortality. However, the exact mechanisms remain unclear. Recent studies have revealed that particulate air pollution exposure is associated with indicators of autonomic function including heart rate, blood pressure, and heart rate variability. However, this association has not been dearly demonstrated in animal studies. To overcome the problems of wide variations in diseased animals and circadian cycles, we adopted a novel approach using a mixed-effects model to investigate whether ambient particle exposure was associated with changes in heart rate and blood pressure in pulmonary hypertensive rats. Male Sprague-Dawley rats were implanted with radiotelemetry devices and exposed to concentrated ambient particles generated by an air particle concentrator. The rats were held in nose-only exposure chambers for 6 hr per day for 3 consecutive days and then rested for 4 days in each week during the experimental period of 5 weeks. These animals were exposed to concentrated particles during weeks 2, 3, and 4 and exposed to filtered air during weeks 1 and 5. The particle concentrations for tested animals ranged between 108 and 338 [micro]g/[m.sup.3]. Statistical analysis using mixed-effects models revealed that entry and exit of exposure chamber and particle exposure were associated with changes in heart rate and mean blood pressure. Immediately after particle exposure, the hourly averaged heart rate decreased and reached the lowest at the first and second hour of exposure for a decrease of 14.9 (p < 0.01) and 11.7 (p = 0.01) beats per minute, respectively. The hourly mean blood pressure also decreased after the particle exposure, with a maximal decrease of 3.3 (p < 0.01) and 4.1 (p < 0.01) mm Hg at the first and second hour of exposure. Our results indicate that ambient particles might influence blood pressure and heart rate. Key words: ambient particles, blood pressure, heart rate, pulmonary hypertension, radiotelemetry. Environ Health Perspect 111:147-150 (2003). [Online 31 October 2002]

doi:10.1289/ehp.5464 available via http://dx.doi.org/

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Epidemiologic studies have shown that increased concentrations of ambient particles are associated with cardiovascular morbidity and mortality (1,2). However, the mechanisms of such associations have not been clearly defined. Recent epidemiologic studies have found associations of increased air particles with increased heart rate and blood pressure and decreased heart rate variability (3-6). It has been speculated that particles cause the activation of autonomic nervous system, leading to changes in heart rates (7). To clarify the relationship of particles with mortality and morbidity, animal models have been used to investigate the effects of particles (8,9). Preliminary studies revealed increased heart rates and arrhythmia in pulmonary hypertensive rats after exposure to concentrated ambient particles (8,10,11). However, a recent study revealed a decreased heart rate when residual oil fly ash was instilled into the rats (12). To investigate further the mechanisms of particle-induced cardiotoxicity, we used heart rate and blood pressure as outcome indicators to assess their association with concentrated ambient particles in pulmonary hypertensive rats. Studies have also indicated that particles with aerodynamic diameter < 2.5 [micro]m (P[M.sub.2.5]) exert greater adverse health effects than coarse particles (1,13). To investigate the effects of P[M.sub.2.5] on cardiovascular diseases, we used an ambient particle concentrator, which generated P[M.sub.2.5], to test our hypothesis (14).

It is a common practice to divide experimental animals into exposure and control groups to study the effects of air particles. Because of the wide variation among diseased animals, this method requires large numbers of animals to delineate the true effect of air particles (9). …

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