Microvascular permeability changes in ischemia/reperfusion injury in the ascending colon of horses

The normal microvascular permeability of the ascending colon in horses and the microvascular permeability of that segment after ischemia and reperfusion were investigated. Microvascular permeability was estimated by the ratio of lymphatic protein to plasma protein concentration (Cl/Cp) at high lymph flow rates in 8 adult horses in 2 equal groups: normal and ischemic (2-hour period). Lymphatic flow rates and lymph and plasma protein concentrations were determined. Intestinal biopsy specimens were obtained at the end of each experiment. Flow independent values were selected and compared by one-way ANOVA, and the mean and SEM of these values were determined. The mean Cl/Cp ratios for the flow independent part of each data set were as follows: normal = 0.36 +/- 0.08; ischemic = 0.70 +/- 0.08. These groups were significantly different (P < or = 0.0001). Microscopic evaluation revealed mild congestion and edema in the normal group. The ischemic group had mild to moderate mucosal degeneration, with moderate to severe congestion and edema. We concluded that ischemia of the ascending colon, when followed by reperfusion, results in a significant increase in microvascular permeability.