Effects of heparin, venous strangulation obstruction of the small intestine, and reperfusion of the small intestine on plasma diamine oxidase activity in horses.

This research article reviews the role of an enzyme called diamine oxidase (DAO), which originates in the small intestine, and its response to various conditions in horses. Tests involving the use of heparin, a type of blood thinner, along with surgical interventions, were conducted to study changes in DAO levels under different circumstances.

Background and Objectives

• The study revolves around the behavior of an enzyme called Diamine Oxidase (DAO). DAO is produced in the small intestine and can be released into the bloodstream by the intravenous administration of heparin. As such, DAO activity can function as an indicator of intestinal health and functionality. Accordingly, two main types of DAO activity are measured in the study: baseline DAO activity, which exists without the administration of heparin, and Postheparin DAO (PHD) activity, which is the DAO activity registered after heparin administration.
• The study’s primary aim is to understand changes in PHD activity during and following small intestine surgery. More specifically, the study looks into the effects of venous strangulation obstruction (VSO) – a severe form of intestinal injury in horses – on the activity of the DAO enzyme.

Study Design and Groups

• The research includes three different groups of horses for study, with each group representing different varying conditions for comparison. One set of conscious horses received two doses of heparin without undergoing any surgery. The second group underwent sham (placebo) small intestinal surgery, while the third group experienced VSO for 90 minutes followed by a reperfusion period – that is, restoration of blood flow – for another 90 minutes.

Key Findings and Observations

• The results showed that the changes in DAO activity after administering heparin in conscious horses were similar to what has been observed in other species. However, in horses subjected to VSO and reperfusion, both the baseline and postheparin DAO activities did not exhibit the expected changes following small intestinal obstruction and injury.
• Interestingly, at the 15-minute mark during the VSO, DAO activity in the blood was significantly higher than in sham-operated controls.

Implications and Conclusion

• The study’s findings suggest that DAO response in horses is similar to other mammals upon heparin administration, which reconfirms DAO as an indicator of intestinal health across various species.
• The lack of expected changes in DAO activity following small intestinal vascular obstruction suggests that horses might respond differently to intestinal injury than other animals. Such findings could have potential implications in devising specific veterinary treatment regimens for horses dealing with similar medical conditions.