Plasma volume, electrolyte, and endocrine changes during onset of laminitis hypertension in horses.

This research investigates the changes in plasma volume, electrolyte levels, and hormones in adult horses during the onset of laminitis, a painful disease affecting the horse’s feet, triggered by carbohydrate overloading in the gastrointestinal tract.

Research Methodology and Results

• To study the onset of the disease, the researchers overfed 12 adult horses with carbohydrates. The horses eventually developed Obel grade 3 (OG3) lameness, equivalent to severe laminitis approximately 40 hours after overfeeding.
• Interestingly, at the onset of this OG3 lameness, a significant decrease in plasma volume was recorded as compared to the base-line values.
• Before the horses reached the OG3 lameness stage, transient deceases in serum phosphorus and calcium were observed. In addition, mild hyponatremia, a condition characterized by low sodium levels, developed and persisted in the horses.
• Upon the establishment of OG3 lameness, two noticeable changes were monitored. Persistent hypokalemia – lower potassium levels in blood, and a concurrent increase in plasma aldosterone concentration – a hormone which helps regulate salt and water balance in the body.
• During the syndromal phase, the research also recorded a transient increase in cortisol and renin activity and a brief occurrence of hypochloremia – less than normal level of chloride in the blood.

Discussion of Findings

• The researchers discussed these changes in plasma volume and serum electrolytes, and their involvement in the progression of acute equine laminitis.
• The study also examined elevated renin activity – which regulates blood pressure and fluid balance, and high aldosterone concentration. These were interpreted as the body’s homeostatic adjustments to the fluid and electrolyte imbalances caused by the disease.
• Finally, they contrasted the differences observed in the development of alimentary laminitis between horses and ponies.

In conclusion, the study provided insight into the physiological changes during the onset of laminitis due to carbohydrate overloading in horses, highlighting its impact on plasma volume, electrolyte balance, and hormone regulation.