Nitric oxide donors as treatment for grass induced acute laminitis in ponies.

This research article investigates the potential role of nitric oxide (NO) donors in treating acute laminitis in ponies. It finds promising evidence that intravenous infusion of l-arginine, a precursor of NO, can cause vasodilation in the hoof and reperfusion of laminal tissues in acutely laminitic ponies.

Overview of Acute Equine Laminitis

• Laminitis is a painful and sometimes deadly condition that affects horses’ hooves. It can be triggered by various factors and causes inflammation of the laminae, tissues connecting the hoof wall to the bone inside.
• Despite intense research efforts, the pathogenesis of laminitis remains only partly understood. This study explores the potential involvement of the arginine-nitric oxide (NO) system, which plays a critical role in regulating blood flow.

Nitric Oxide and Vasodilation

• Nitric oxide, produced from the amino acid l-arginine by NO synthase (NOS) enzyme, functions as a vasodilator. It relaxes the smooth muscle in blood vessel walls, allowing the vessels to dilate (expand) and increase blood flow.
• The authors hypothesise that a blunted vasodilatory response could contribute to laminitis. To investigate this, they infused 10% l-arginine into healthy and laminitic ponies.
• The results showed noticeable vasodilation in the hoof of a healthy pony. In a laminitic pony, it led to immediate reperfusion (restoration of blood flow) in the affected laminal tissues. The authors used near-infrared spectroscopy (NIRS), a non-invasive technique, for monitoring these changes.

Potential Treatment for Acute Laminitis

• Based on their findings, the authors suggest that NO donors could serve as a therapeutic option for acute laminitis. They examined the effects of glyceryl trinitrate, a popular NO donor drug.
• When applied topically to the pastern (the part of a horse’s foot between the hoof and the fetlock), glyceryl trinitrate reduced the lameness commonly observed in laminitic horses. It also ‘diluted the bounding pulses’ commonly associated with the disease and lowered overall blood pressure.
• These results imply that increasing nitric oxide in the blood can be beneficial for managing laminitis symptoms by restoring blood flow in the affected tissues, thus presenting a possible method of treatment.