Changes in blood neutrophil/lymphocyte ratio related to adrenocortical function in the horse.

This research studied how activities like hormone injection and exercise in horses can affect the ratio of neutrophils to lymphocytes in their blood, and found that both activities led to a significant increase in this ratio.

Study Design and Participants

• The study was conducted on 8 Thoroughbred horses, with each undergoing two different types of interventions: the injection of adrenocorticotrophic hormone (ACTH1-24), and a physical exercise routine.
• Measurements of blood neutrophil/lymphocyte ratio and plasma cortisol levels were taken before and after each intervention.

Effects of ACTH1-24 Injection

• The researchers observed a significant increase in plasma cortisol levels within 60 minutes of the ACTH1-24 injection.
• The neutrophil/lymphocyte ratio also altered significantly, with the change observable at 240 minutes after the hormone injection.
• This suggests a connection between adrenocortical function (as indicated by cortisol levels) and the ratio of neutrophils to lymphocytes in the blood, following a hormone injection.

Effects of Exercise

• When subjected to a training gallop exercise, the horses also showed a significant immediate increase in plasma cortisol levels.
• Changes in the neutrophil/lymphocyte ratio were noted at 180 minutes after the exercise, with the ratio significantly increasing.
• The study also found a transient increase in the number of lymphocytes in the blood (lymphocytosis) after the exercise.

Interpretation of Findings

• The increase in cortisol levels after both interventions suggests that both activities stress the adrenocortical function, triggering the release of the hormone.
• The shifts in the neutrophil/lymphocyte ratio are associated with this same stress, likely as part of the immune system’s response.
• The occurrence of lymphocytosis after exercise could be another aspect of the immune response, temporarily increasing the pool of these cells in the bloodstream in reaction to the physical stress caused by exercise.