Effect of ischemia and reperfusion on oxidative processes in the large colon and jejunum of horses.

OBJECTIVE

To evaluate and compare oxidative processes during ischemia and reperfusion of the equine large colon and jejunum.

ANIMALS

2 groups of 6 anesthetized horses undergoing a terminal procedure.

PROCEDURE

Isolated loops of large colon and jejunum were subjected to 2 hours of ischemia, followed by 2 hours of reperfusion. Tissue specimens were taken after 105 minutes of ischemia and 10, 30, 60, and 120 minutes of reperfusion. Mesenteric arterial and venous blood samples were collected for blood gas analysis at the same times to evaluate ischemia and reoxygenation. Oxidative processes in tissues were evaluated by use of biochemical assays for malondialdehyde and conjugated dienes and by use of the manganese-diaminobenzidine histochemical technique for localized superoxide generation.

RESULTS

Significant quantities of malondialdehyde and conjugated dienes were detected in the jejunum after 60 and 120 minutes of reperfusion together with histochemical evidence of superoxide generation in jejunal endothelial cells and in submucosal neutrophils and eosinophils.

CONCLUSIONS

Oxidative processes do not appear to have an appreciable role in inducing damage in the equine large colon during reperfusion after 2 hours of ischemia. In contrast to the jejunum, reactive oxygen species are not generated in measurable quantities in the large colon subsequent to ischemia and reperfusion.

CLINICAL RELEVANCE

Free radical scavengers are not likely to be effective in prevention of equine colonic mucosal deterioration after ischemia.