Effect of pleuran (beta-glucan from Pleurotus ostreatus) in diet or drinking fluid on colitis in rats.

The effects of pleuran, beta-glucan isolated from Pleurotus ostreatus, were studied in a model of acute colitis in rats. Pleuran was given either as a 2% food component or as 0.44% pleuran hydrogel drink over 4 weeks. Colitis was induced by intraluminal instillation of 4% acetic acid and after 48 h the extent of colonic damage and several biochemical parameters were examined. Pleuran supplementation both in food and in drinking fluid significantly decreased the disposition to colitis. The macroscopic damage score was reduced by 51% or 67% by pleuran diet and pleuran hydrogel drink, respectively. Pleuran did not influence the final body weights of rats but prevented significantly colonic wet weight increase which was observed in the control diet group. The enhanced activity of myeloperoxidase in the inflamed colonic segment was reduced by pleuran diets, reflecting decreased neutrophil infiltration. The colonic damage was accompanied by decreased activities of lysosomal enzymes--acid phosphatase and cathepsin D--in the control untreated group, whereas in the pleuran groups the decrease was significantly attenuated. Both pleuran regimens reduced the content of conjugated dienes in the colon, liver and erythrocytes. In contrast to this fact, activities of antioxidant enzymes in erythrocytes and the colon were not so greatly influenced. Significant increase was found only in the case of SOD activity in sham operated rat erythrocytes under influence of both pleuran regimes and in the case of GST activity in erythrocytes of pleuran hydrogel group. The mechanism of the described protective effect of pleuran is not yet fully understood. Our results indicate that the pleuran-enhanced antioxidant defence of the colonic wall against the inflammatory attack may have come into play.