Effects of the addition of endotoxin during perfusion of isolated forelimbs of equine cadavers.

This study explores the impact of endotoxins on the metabolism and structural changes in isolated horse limbs. The researchers discovered that endotoxin exposure results in significant metabolic changes and alterations in the laminar tissues of the limbs, suggesting endotoxins could be a direct cause, not just a risk factor, for laminitis.

Methodology

• Forelimbs (the metacarpus and digit) were collected from the cadavers of 12 healthy adult horses post slaughter at an abattoir.
• These limbs were perfused for 10 hours with autologous blood, some with and others without the addition of endotoxin (80ng of lipopolysaccharide [LPS]/L).
• To evaluate the impact of body weight on the results, two limbs from the endotoxin exposure group, and two nonperfused limbs were subjected to loading until failure of the pedal bone suspensory apparatus occurred.
• The study monitored and evaluated various metabolic and histologic variables throughout the experimental process.

Results

• During the first hour of the experiment, blood pressure increased but did not vary between the groups.
• Lactate dehydrogenase activity was the same in both groups and increased significantly over the 10-hour period.
• Glucose consumption at the 5-hour point and lactate concentration at the 8-hour mark were significantly higher in the limbs exposed to endotoxin.
• In the limbs exposed to LPS, the width of the secondary epidermal lamellae was greater, and in the primary dermal lamellae, there were significantly more vessels with an open lumen and aggregates of intravascular neutrophils.

Conclusions

• The study concluded that in the blood-perfused isolated limbs of equine cadavers, exposure to LPS resulted in significant changes in the laminar tissue as well as in metabolic alterations.
• These findings suggest that endotoxins should be viewed as a potential causal factor for laminitis, as opposed to being merely a risk factor.