Measurement of erythrocyte volumes in splenectomized horses and sham-operated horses at rest and during maximal exercise.

This research study examined the volumes of erythrocytes, or red blood cells, in thoroughbred horses, and determined the impact of the spleen on erythrocyte volumes during rest and maximal exercise. It was observed that the method used to tag erythrocytes with the non-radioactive isotope, 50Cr, provided accurate measurements of erythrocyte volumes, showing that splenectomized horses had slightly smaller plasma volumes during maximal exercise compared to those at rest.

Overview of study methodology and outcomes

• The research investigated the erythrocyte volumes in both splenectomized horses (those who had their spleens removed) and sham-operated horses, which served as the control group.
• To tag the erythrocytes and allow for tracking, a non-radioactive isotope, 50Cr, was injected into the horses two hours before measurement. This allowed for the detection and measurement of the volume of red blood cells in the horses’ circulatory systems.

Erythrocyte volumes findings

• It was observed that in sham-operated horses (those with intact spleens), the erythrocyte volumes did not increase as expected during maximal exercise, but remained about the same as when at rest. This was contrary to the presumption that the spleen would release erythrocytes into the bloodstream during intensive activity.
• Interestingly, in the splenectomized horses, erythrocyte volumes at rest and during exercise were also almost equal, suggesting that the spleen may not play as significant a role in erythrocyte release as previously thought.

The role of the spleen in plasma volumes

• However, it was found that the plasma volumes of the splenectomized horses during maximal exercise were slightly smaller than those at rest. This indicates that the presence of the spleen may contribute to maintaining plasma volume during intense activity.
• Furthermore, in sham-operated horses, there was a significant decrease in plasma volume post-exercise, suggesting the spleen may also be involved in the process by which plasma disappears from the bloodstream during physical stress.

Final Remarks

• This study showed the possibility of tracking and measuring erythrocyte volumes using the 50Cr-tagging method. This can potentially offer a unique way of investigating equine blood physiology and the role of the spleen in erythrocyte and plasma volume regulation.