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Pulmonary Sensitivity to Ozone Exposure in Sedentary Versus Chronically Trained, Female Rats
Citation:
Gordon, C., P. Phillips, T. Beasley, A. Ledbetter, A. Cenk, U. Kodavanti, AND A. Johnstone. Pulmonary Sensitivity to Ozone Exposure in Sedentary Versus Chronically Trained, Female Rats. INHALATION TOXICOLOGY. Informa Healthcare USA, New York, NY, , 293-302, (2016).
Impact/Purpose:
This study represents the first attempt to develop an animal model of an active versus sedentary life style and how it may affect the susceptibility to an air pollutant. In other words, the study treated a sedentary life style as a "non-chemical" stressor. Female rats were allowed to train on running wheels for 12 weeks, representing an active life style. Sedentary animals were housed in cages without wheels. The pulmonary, behavioral,and metabolic responses to weekly ozone exposure (6 weeks) were assessed in the active and sedentary rats. Exercise training afforded some protection to the pulmonary effects of ozone. These animals were also less affected by the weight loss impact of ozone exposure. On the other hand, sedentary rats exhibited some protection from some protein markers of pulmonary inflammation. Allowing rats to continue running on wheels after ozone exposure may have exacerbated some of the inflammatory effects of ozone. Overall,active lifestyle may provide protection to ozone exposure.
Description:
Epidemiological data suggest that a sedentary lifestyle may contribute to increased susceptibility to some environmental toxicants. The lack of adequate exercise combined with poor dietary choices are considered to be primary causes of obesity. To study the impact of an active versus sedentary lifestyle on susceptibility to air pollution,we developed an animal model 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 (03 for 5 hr/d, 1 d/wk, for 6 wks (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 03 and 24 hr after the 5th Q3 exposure. Trained rats lost -2% body fat and had significant reductions in Penh, minute ventilation, and frequency after 12 wk of access to running wheels. Peak wheel activity was reduced by 40% during the night after exposure to 1.0 ppm 03. After the 5th 03 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 03, suggesting that the training increased pulmonary resistance from Q3. However, lung lavage cell counts and biomarkers of pulmonary inflammation measured 1 day after the final exposure were inconsistently affected by training. Chronic, voluntary wheel running activity led to marked physiological responses to female rats along with some indication of improved pulmonary recovery from 03 exposure. However, continued training with 03 exposure may also be a detriment for some pulmonary endpoints. Overall, a sedentary lifestyle may increase pulmonary and metabolic susceptibility to Q3 but additional studies are needed.
