Short-term incubation of equine laminar veins with cortisol and insulin alters contractility in vitro: possible implications for the pathogenesis of equine laminitis.

The researchers conducted an experiment to study the impact of cortisol and insulin on the contractility of healthy small laminar veins in horses, and they suggest implications in the development of equine laminitis, a condition causing severe lameness and pain in horses.

Research Methods

• The study involved the incubation of equine laminar veins (with a diameter ranging from 150-500 μm) with cortisol and insulin, hormones which are known to impact both blood sugar levels and vascular function.
• The veins used in the experiments were extracted from healthy horses or ponies from the digital laminae. The veins’ behaviors were studied through wire myography.
• Researches constructed concentration response curves for noradrenaline (NA), phenylephrine (PE), endothelin-1 (ET-1), and 5-hydroxytryptamine (5-HT) when these enzymes were present along with cortisol or insulin.

Key Findings

• Cortisol notably increased the maximum contractility of laminar veins to the vasoconstrictors NA and 5-HT, implying a potential elevated risk for venoconstriction and, consequently, laminitis.
• However, cortisol was found to decrease the highest contraction to ET-1, another vasoconstrictor.
• Insulin, on the other hand, led to a decrease in contractility of veins in response to PE and ET-1.
• The existence of insulin resistance, which reduces insulin’s ability to counteract alpha-adrenoreceptor and ET-1-mediated contraction, may compound the effect of venoconstriction, leading to a higher susceptibility to laminitis.

Implications

• The results of the study suggest that animals experiencing short-term cortisol excess might be prone to an increased venoconstrictor response to 5-HT and NA, thereby predisposing these animals to laminitis.
• The findings also indicate that disorders such as equine Cushing’s disease and equine metabolic syndrome, both of which can be associated with hormonal imbalances and insulin resistance, may lead to a heightened risk for laminitis in horses.