Effect of furosemide on plasma atrial natriuretic peptide and aldosterone concentrations and renin activity in running horses.

The research investigates whether furosemide, a common diuretic drug, affects the concentration of certain hormones and enzymes (atrial natriuretic peptide, renin, and aldosterone) in the plasma of horses during submaximal exercise.

Study Design and Implementation

• The study involved six mares (adult female horses) that were not acclimated to exercise.
• Each horse was run on a treadmill for 60 minutes at a submaximal intensity, approximating the heart rate at 65% of maximum following a saline treatment.
• The mares were either given furosemide (1 mg/kg of body weight) or a heparinized saline solution intravenously either 4 hours or 2 minutes before the exercise period.

Effects of Furosemide on Hormones and Enzymes

• Furosemide was found to suppress the exercise-induced increase in plasma atrial natriuretic peptide (ANP) concentrations. ANP is a hormone that influences blood pressure and the balance of water and salt in the body.
• The mean ANP concentration 15 minutes into the running period was 63.9 pg/ml with furosemide treatment as compared to 100 pg/ml with saline treatment.
• The drug boosted the response of renin activity to exercise. Renin is an enzyme involved in the body’s fluid balance and blood pressure regulation systems. Its plasma concentrations increased to a higher extent following furosemide treatment (18.6 ng/ml/h) than with saline treatment (6.0 ng/ml/h).
• There was no discernible impact of furosemide on the exercise-induced increase in plasma aldosterone concentration. Aldosterone is a hormone that regulates salt and water balance in the body.

Interpretation

• The effects of furosemide on these vital body regulation systems in horses during exercise are significant, as this drug is often used to prevent internal bleeding in racehorses. However, as seen in this study, the dosage can influence the balance of enzymes and hormones involved in the body’s fluid balance and blood pressure regulation, potentially affecting the horses’ health and performance.
• While the study didn’t find any effect of furosemide on the aldosterone concentration, the channges it induced in the levels of ANP and renin during exercise can still be significant if considering the drug for use in racehorses or other working horses.