Guinea pig lung inflammatory cell changes following acute ozone exposure

The time course of inflammatory cell infiltration into guinea pig lungs following a single 4 h exposure to 2 ppm O3 was established by measuring the changing cell populations recovered by both bronchoalveolar lavage (BAL) and collagenase tissue digestion. Analysis of BAL-recovered albumin was used as an indicator of permeability damage and demonstrated an increase immediately following ozone exposure, reaching a maximum within 24 h, but returning to air-control levels by 7 days post-ozone exposure. A twofold enhancement in macrophages was observed in the lavage-recovered cell population after 2 days, returning to air-control numbers by 7 days. Collagenase digest-recovered monocytes and macrophages, identified by nonspecific esterase staining, were found to be elevated between 2 and 14 days following O3 exposure. Immediately following O3 exposure, a 4.5-fold increase in collagenase digest-recovered neutrophils was observed, with a subsequent decline to air-exposed lung levels during the next 12 h. In contrast, BAL-recovered neutrophils were observed to be increased immediately following O3 exposure at a level that was sustained for up to 3 days. The tissue accumulation of neutrophils was not associated with their subsequent appearance in the lavageable spaces. Although significant increases in collagenase digest-recovered eosinophils could not be detected, lavage-recovered eosinophil numbers were transiently increased by threefold after 3 days. By employing both BAL and collagenase digestion to evaluate this model of reversible lung injury, this study demonstrated that the use of BAL-recovered cell measurements alone does not adequately reflect the early inflammatory cell changes taking place within oxidant-exposed lungs.