Effects of acute intravenous aldosterone administration on Na(+), K(+), and water excretion in the horse.

This research study explored how a short-term increase in the hormone aldosterone, administered intravenously, impacts the excretion of sodium, potassium, and water in horses. The findings showed that increased aldosterone reduces sodium loss via urine and feces but doesn’t alter sweat composition, with feces identified as the primary pathway for aldosterone excretion.

Methods

• The study was carried out on four horses.
• Aldosterone was given to each horse intravenously, at 20-minute intervals over 6 hours. The total amount given was 5.4 micrograms per kilogram of the horse’s body weight.
• The researchers collected data on sodium, potassium, and water excretion in the horses before, during, and for 48 hours after the administration of aldosterone.
• In a second part of the study, some horses were exercised after the aldosterone treatment, and some were exercised without prior treatment.
• Sweat samples were collected from the exercised horses and analyzed.

Results

• The researchers found that the administration of aldosterone greatly reduced the loss of sodium through urine and feces by 99% and 72% respectively. This was followed by a significant increase in sodium excretion through both mediums later on.
• Fecal potassium excretion increased in the first six hours following treatment, and the concentration of potassium in plasma dropped.
• The horses retained fluids during the treatment and for approximately 12 to 15 hours after.
• No changes were observed in the composition of sweat after the administration of aldosterone.

Conclusions

• The study concluded that acute injections of aldosterone reduce losses of sodium in feces and urine, but not in sweat.
• The researchers also identified feces as the primary pathway of aldosterone excretion.