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

The research study investigates how lack of blood flow (ischemia) and return of blood flow (reperfusion) affects oxidative processes in the large colon and jejunum of horses. It concludes that unlike the jejunum, oxidative processes do not play a significant role in damage to the large colon during reperfusion after ischemia.

Study Design and Methods

• The study involved two groups of six anesthetized horses which were subject to a terminal procedure.
• Isolated loops from the large colon and jejunum of these horses were subjected to two hours of ischemia, which involved restricting blood flow, followed by two hours of reperfusion or return of blood flow.
• Tissue samples were collected at different time intervals during the process, specifically after 105 minutes of ischemia and at 10, 30, 60, and 120 minutes of reperfusion.
• Blood samples from the mesenteric arterial and venous sources were also collected at these same time intervals. They were then analyzed specifically for the level of oxygen (ischemia and reoxygenation).
• The oxidative processes in the tissues were evaluated using a range of biochemical assays and techniques.

Results

• The study found that significant amounts of malondialdehyde and conjugated dienes, by-products indicative of oxidative stress, were found in the jejunum after 60 and 120 minutes of reperfusion. There was also visible evidence of superoxide generation in various cells within the jejunum.
• In contrast, the same oxidative processes did not seem to be occurring in the large colon under the same conditions.

Conclusions

• The findings suggested that oxidative processes, while important in the jejunum, do not seem to play an important role in damage to the large colon during reperfusion after ischemia.
• Unlike the jejunum, reactive oxygen species, which are indicative of an oxidative process, are not generated in measurable quantities in the large colon after ischemia and reperfusion.
• The study therefore concludes that free radical scavengers, which are typically used to counteract oxidative damage, are unlikely to be effective in preventing mucosal deterioration in the equine large colon following ischemia.