QUANTIFICATION OF TISSUE-DAMAGE IN THE FELINE SMALL-INTESTINE DURING ISCHEMIA-REPERFUSION - THE IMPORTANCE OF FREE-RADICALS

Intestinal ischaemia is accompanied by characteristic mucosal lesions, which can be graded according to a six-grade system proposed by Chiu et al. (1970). This report describes a continuous grading system which makes it possible to quantify the intestinal damage in connection wit h ischaemia-reperfusion. The present morphometric method is based on q uantitative histological analysis of intestinal biopsies performed on 200 histological sections from 44 cat experiments. Radical formation w as quantified by infusing close i.a. a spin trap, OXANOH, which produc es a secondary stable radical, OXANO, after reacting with radicals in the tissue. OXANO concentration was determined in venous blood samples with electron spin resonance. We demonstrate a highly significant cor relation between the grading system of Chiu et al. (1970) and the morp hometric analysis of this study. The tissue damage was located exclusi vely in the intestinal villi. Comparing the mucosal damage that occurs during 60 min of intestinal ischaemia (superior mesenteric artery pre ssure 15-25 mmHg) with that seen during the first 30 min reperfusion t his study shows that the villus damage occurring during ischaemia is a t least twice as large as the aggravation seen upon reperfusion. Furth ermore, the authors demonstrate a significant correlation between rate of radical formation and villus tissue damage particularly during the first 30 min after ischaemia. It is concluded that the proposed quant itative morphological method represents a nondiscrete grading system f or evaluating tissue damage in connection with ischaemia-reperfusion i n the small intestine. The ischaemia itself inflicted a more severe da mage to the intestine than reperfusion. A significant correlation betw een damage and radical formation was demonstrated during the reperfusi on. However, the results suggest that factors other than radical forma tion are of importance in explaining the tissue damage upon reperfusio n. The nature of these factors is presently unknown.