Hog barn dust extract increases macromolecular efflux from the hamster cheek pouch

Departments of 1 Medicine and 2 Biopharmaceutical Sciences, Colleges of Medicine and Pharmacy, University of Illinois at Chicago, and 3 Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois; and 4 Department of Internal Medicine, University of Nebraska Medical Center, Omaha, Nebraska Submitted 7 September 2005 ; accepted in final form 15 February 2006 The purpose of this study was to determine whether short-term exposure to an aqueous extract of hog barn dust increases macromolecular efflux from the intact hamster cheek pouch and, if so, to begin to determine the mechanism(s) underlying this response. By using intravital microscopy, we found that suffusion of hog barn dust extract onto the intact hamster cheek pouch for 60 min elicited a significant, concentration-dependent leaky site formation and increase in clearance of FITC-labeled dextran (molecular mass, 70 kDa). This response was significantly attenuated by suffusion of catalase (60 U/ml), but not by heat-inactivated catalase, and by pretreatment with dexamethasone (10 mg/kg iv) ( P < 0.05). Catalase had no significant effects on adenosine-induced increase in macromolecular efflux from the cheek pouch. Suffusion of hog barn dust extract had no significant effects on arteriolar diameter in the cheek pouch. Taken together, these data indicate that hog barn dust extract increases macromolecular efflux from the in situ hamster cheek pouch, in part, through local elaboration of reactive oxygen species that are inactivated by catalase. This response is specific and attenuated by corticosteroids. We suggest that plasma exudation plays an important role in the genesis of upper airway dysfunction evoked by short-term exposure to hog barn dust. microcirculation; postcapillary venules; reactive oxygen species; catalase; dexamethasone; plasma exudation; fluorescein isothiocyanate-labeled dextran Address for reprint requests and other correspondence: I. Rubinstein, Dept. of Medicine (M/C 719), Univ. of Illinois at Chicago, 840 South Wood St., Chicago, IL 60612-7323 (e-mail: IRubinst{at}uic.edu )