Dexamethasone attenuates grain sorghum dust extract-induced increase in macromolecular efflux in vivo

The purpose of this study was to determine whether dexamethasone attenuates grain sorghum dust extract-induced increase in macromolecular efflux from the in situ hamster cheek pouch and, if so, whether this response is specif ic. By using intravital microscopy, we found that an aqueous extract of gra in sorghum dust elicited significant, concentration-dependent leaky site fo rmation and increase in clearance of FITC-labeled dextran (FITC-dextran; mo l mass, 70 kDa) from the in situ hamster cheek pouch (P < 0.05). This respo nse was significantly attenuated by dexamethasone (10 mg/kg iv). Dexamethas one also attenuated substance P-induced leaky site formation and increase i n clearance of FITC-dextran from the cheek pouch but had no significant eff ects on adenosine-induced responses. Dexamethasone had no significant effec ts on arteriolar diameter in the cheek pouch. On balance, these data indica te that dexamethasone attenuates grain sorghum dust extract- and substance P-induced increases in macromolecular efflux from the in situ hamster cheek pouch in a specific fashion.