Plasma exudation, hyperaemia, and epithelial permeability in rats with oxazolone-induced colitis: Modulatory effects of budesonide

Background: Oxazolone-induced colitis in the rat is an immune-driven model of human colitis. The aim of the present study was to measure the changes i n the absorptive and exuadative permeabilites, oedema formation, and local blood How in this model during the development of inflammation. We also ass essed the effects of acute (<1 h). topical glucocorticosteroid (GCS) treatm ent on these factors. Methods: Colitis was induced by local instillation of oxazolone in previously sensitized animal. Calculating the 40-min plasma-e quivalent extravascular volume quantitated the plasma exudation rate. This was derermined by using labelled albumin as marker for total tissue content of plasma and Evans blue content as marker fur the intravascular volume. A bsorptive permeability was simultaneously measured as uptake of rectally ad ministered (Cr-51)-labelled ethylenediaminetetraacetic acid (EDTA). In sepa rate experiments regional blood Hows were measured by means of the labelled microsphere method. Results: At both 3 and 24h after challenge marked enha ncements of both exudative and absorptive permeabilities were found. At 24 h there was also an increase in local blood flow. GCS treatment abolished a ll of the hyperaemia and the: main parr of the exudative response but had n o significant effect on the absorptive permeability. Conclusions: In this m odel immunologic mechanisms induce permeability and blood now changes simil ar to those in the human disease. It seems suitable for the study of GCS an d other anti-inflammatory or immune-modulating drugs.