El ejercicio físico aumenta el daño pulmonar inducido por la exposición aguda e intermitente a 0,5 ppm de ozono en ratas juveniles

Abstract

Tropospheric ozone (O3) is the major oxidant of photochemical smog. Being an air pollutant, its effects are related to effective dose = [Concentration] x [exposure time] x [pulmonary ventilation]. Objective: Determine whether physical exercise -that increases pulmonary ventilation- is able to augment the pulmonary damage induced by O3 exposure in resting rats. Material and Methods: Four series of juvenile Sprague-Dawley rats were used. Two series were exposed to 0.5 ppm O3 (4 hours a day for 2 days) at rest (n=13) or during exercise (n=12). Two control series breathed filtered air (FA) at rest (n=13) or during exercise sessions (n=13), in a vertical rotary wheel (15 min exercise alternated with 15 min resting until to completing 4 hours a day for 2 days). Rats were euthanized and wet weight / dry weight ratio (W/D ratio) was determined in left lung. Total cell counting, total protein content and γ-glutamyltraspeptidase (GGT) activity were determined in the right lung bronchoalveolar lavage fluid (BALF). Results: W/D weight ratio as well as total cell counting and protein content increased in BALF from resting rats exposed to O3 as compared with resting rats breathing FA (p < 0.05 ANOVA & Newman-Keuls test). GGT activity in BALF increased in rats under exercise breathing FA as compared with resting rats breathing FA (p<0.05). GGT, proteins and cells counting increased in BALFfrom series [exercise + O3] as compared to series [resting + O3] (p< 0.05). Conclusion: Physical exercise increases lung damage induced by intermittent and acute 0.5 ppm O3 exposure in juvenile rats.