Microvascular permeability and endothelial cell morphology associated with low-flow ischemia/reperfusion injury in the equine jejunum.

The research study investigates how low-flow ischemia (25% reduction in blood flow) and reperfusion (restoration of blood flow) affects the microvascular permeability, or the capacity of small blood vessels to let in substances, of the jejunum, a part of the small intestine, in horses. The study also examines associated effects on endothelial cell morphology, or structured changes in the cells lining the blood vessels, during an episode of ischemia/reperfusion injury. The findings suggest that ischemia/reperfusion injury causes a significant increase in the microvascular permeability of the equine jejunum and leads to structural damage in the capillary endothelial cells.

Approach and Study Groups

• The research involved eight adult horses, randomly allocated to two equal groups: a normal group and an ischemic/reperfusion injury group.
• Core experimental factors like lymphatic flow rates, mesenteric blood flow, and lymph and plasma protein concentrations were determined at intervals of fifteen minutes throughout the study.
• Microvascular permeability was evaluated by estimating the osmotic reflection coefficient, essentially measuring the proportion of protein substances passing from the blood plasma into the lymph fluid.

Measurements and Determination of Ischemia/Reperfusion Injury

• The osmotic reflection coefficient for normal equine jejunum was found to be 0.19 +/- 0.06, and it significantly increased to 0.48 +/- 0.05 after the ischemia/reperfusion period, indicating an increase in microvascular permeability.
• Biopsy specimens from the jejunum were taken before and after each experiment to estimate tissue volume (which would highlight edema or swelling due to fluid) and to examine the morphology of the capillary endothelial cells under a transmission electron microscope.

Evidence of Enhanced Microvascular Permeability and Endothelial Damage

• Microscopic evaluation revealed a significant increase in the submucosal (inner layer) and serosal (outer layer) volume of the jejunum, hinting at the presence of edema.
• There was noticeable capillary endothelial cell damage in the horses that underwent ischemia/reperfusion injury, confirming that this process causes cell-level injury.
• The results, therefore, corroborate the hypothesis that ischemia/reperfusion in horses causes a significant increase in the permeability of the microvascular network in the jejunum, and contributes to the damage of the endothelial cells forming these vessels.