Pulmonary sensitivity to ozone exposure in sedentary versus chronically trained, female rats

Abstract

Epidemiological data suggest that a sedentary lifestyle may contribute to increased susceptibility for some environmental toxicants. We developed an animal model of active versus sedentary life style by providing female Sprague-Dawley rats with continuous access to running wheels. Sedentary rats were housed in standard cages without wheels. After training for 12 wks, rats were exposed to 0, 0.25, 0.5 or 1.0 ppm ozone [O3 for 5 h/d, 1 d/wk, for 6 wk (N = 10 per group)]. Body composition (%fat, lean and fluid) was monitored noninvasively over the course of the study. Ventilatory parameters [tidal volume, minute ventilation, frequency and enhanced pause (Penh)] were assessed using whole-body plethysmography prior to O3 and 24 h after the 5th O3 exposure. Trained rats lost ∼2% body fat after 12 wk of access to running wheels. Peak wheel activity was reduced by 40% after exposure to 1.0 ppm O3. After the 5th O3 exposure, body weight and %fat were reduced in sedentary but not trained rats. Penh was significantly elevated in sedentary but not trained rats the day after exposure to 1.0 ppm O3. However, lung lavage cell counts and biomarkers of pulmonary inflammation measured 1 day after the final exposure were inconsistently affected by training. Wheel running led to marked physiological responses along with some indication of improved pulmonary recovery from O3 exposure. However, wheel running with O3 exposure may also be a detriment for some pulmonary endpoints. Overall, a sedentary lifestyle may increase susceptibility to O3, but additional studies are needed.

Active vs. sedentary lifestyle from weaning to adulthood and susceptibility to ozone in rats

“…We found a significant increase in Penh after the first and second exposure to 1.0 ppm ozone; however, there was no effect of exercise training on this this response. This was surprising since we recently reported that the ozone-induced rise in Penh of Sprague-Dawley rats exhibited a beneficial effect in response to exercise training (11). In that study, Penh was measured the day after ozone exposure.…”

“…Overall, rats were studied in blocks of 20 each day over a 1-wk period with all animals exposed to ozone, tested for ventilatory function and glucose tolerance, and terminated. We chose a maximum ozone concentration of 1.0 ppm with the expectation that this concentration in other rat strains would evoke profound pulmonary inflammatory responses as we have shown in previous studies using concentrations of 0.8 -1.0 ppm (11,12). The lower concentrations were selected to develop a doseresponse.…”

“…A few studies have demonstrated improvements in the response to air pollutants and to PCBs (polychlorinated biphenyls) in laboratory rodents subjected to a chronic exercise regimen (21,27). A recent study from our laboratory demonstrated some improvements to ozone-induced changes in ventilation and lipolysis in adult rats that had been allowed access to running wheels for 12 wk (11). However, many of the pulmonary inflammatory markers to ozone were equally affected in sedentary and exercise-trained rats.…”

“…We hypothesized that a sedentary subject with little or no exercise activity would be more susceptible to ozone and other air pollutants, especially pollutants that impact the respiratory and cardiovascular systems. To follow up on our adult rat exercise study described earlier (11), we questioned whether allowing animals to have access to running wheels very early in life (i.e., at weaning) would be more efficacious in terms of attenuating cardiopulmonary responses to ozone. In addition, such a study could highlight the importance of a model of childhood sedentary vs. active lifestyle and effects on susceptibility as an adult.…”

Ozone Exposure, Cardiopulmonary Health, and Obesity: A Substantive Review

“…21 Additional studies have investigated the role of diet and sedentary behavior on ozone exposure responses. 42,43 …”