Distribution of lactate in plasma and erythrocytes during and after exercise in horses.

This research paper investigates how lactate, a substance produced during intensive physical activity, is distributed between plasma and red blood cells in horses both during and after exercise. The study finds that lactate is unequally distributed between the two, a distribution that differs greatly between individual horses and is influenced by factors such as exercise intensity and haematocrit.

Methods and Measurements

• The researchers carefully monitored six Standardbred horses at rest, during an exercise, and 30 minutes post-exercise.
• They measured both lactate and water concentrations in the blood and plasma. These samples were collected before exercise, during the last 15 seconds of each step of an incremental exercise test, and at 5-minute intervals during the first 30 minutes post-exercise.

Main Findings

• Initially, before the exercise routine, the ratio of lactate concentration in red blood cells and plasma were almost equal (ratio was approximately 1.02 +/- 0.34).
• However, during the exercise, lactate accumulated more rapidly in plasma than in red blood cells. The mean lactate concentration in the whole blood was only 59% of that in plasma during the exercise phase.
• The measurements of lactate in whole blood and plasma were found to be highly correlated during exercise. Nonetheless, some deviations were observed when the plasma lactate concentration exceeded 8 mmol l-1.
• There was a notable variation among individual horses with respect to the ratio of lactate concentrations in whole blood and plasma, both during different exercise intensities and at different post-exercise times.

Associated Factors and Variability

• The ratio of lactate amounts in whole blood and plasma was significantly associated with exercise intensity and haematocrit, a measure of the proportion of blood occupied by red blood cells.
• A key finding was that the effects of plasma lactate and haematocrit on the ratio varied greatly among individual horses.
• The distribution of lactate between red blood cells and plasma was markedly inconsistent among horses. This fraction was also greatly influenced by haematocrit.

Conclusion

• The researchers concluded that lactate in horse blood is not evenly distributed between red blood cells and plasma, particularly after immediate centrifugation after collection.
• This inequality is influenced by variables such as haematocrit and shows significant variability among individual horses.