Assessment of microvascular clamping injury of rat aorta by histochemical examination of oxidoreductases

To assess clamping injury to the rat abdominal aorta, the activities of two oxidoreductases, lactate dehydrogenase (LD) and succinate dehydrogenase (SD), were estimated histochemically at various points in time after clamping the aorta for 30 min (group A) or 60 min (group B) with two kinds of microvascular clips. Areas of depressed LD and SD activity were found 3 days after surgery in group A and 1 day and 3 days after surgery in group B. The random, intermittent occurrence of the changes in enzyme activity within the time groups pointed to a mild trauma induced by the clips. At 1 week and thereafter, no changes in enzyme activities were observed in the aortic wall. Two different patterns of depressed enzyme activity were observed: One was a narrow zone without activity throughout the medial layer, and the other consisted of a broader area of depressed activity in the outer parts of the media. Occluding the aorta with a mosquito clamp led to tissue destruction and loss of enzyme activity in the injured area. This study shows that enzyme histochemistry provides nonquantitative methods to detect and localize microvascular injury and that the injury caused by the microvascular clips was mild and reversible.