Clinical, histopathological and metabolic responses following exercise in Arabian horses with a history of exertional rhabdomyolysis.

The research involves studying the reactions of Arabian horses that have experienced exertional rhabdomyolysis (ER) against those that have not using various tests and samples. The tests did not show any marked difference in responses between the two groups, though horses with ER exhibited more unusual features in the microscopic examination of muscle tissues.

Research Details

• The Arabian horses chosen for the research were divided into two groups: those who had previously experienced ER (10 horses) and those who hadn’t (9 horses).
• Following a rest period, these horses were fitted with telemetric ECG machines, and tests were conducted during a 47-minute submaximal standardised field exercise test (SET).
• The horses’ plasma glucose, lactate, electrolyte, and total protein concentrations, as well as their packed cell volume, were measured before and after the exercise.
• The researchers also obtained blood and percutaneous gluteal muscle samples prior to and 3 hours after exercising to evaluate plasma creatine kinase (CK) activity and muscle glycogen concentration, respectively.
• Additionally, a formalin-fixed pre-exercise muscle section was examined under a microscope to identify any abnormalities or signs of disease.
• Analysis of the data was executed through ANOVA and non-parametric tests.

Findings and Conclusion

• No horses showed clinical signs of ER during the exercise, and plasma CK levels rose similarly in both the ER and control groups.
• There were no significant differences in muscle glycogen, heart rate, and other plasma variables between the two groups of horses.
• Horses that had previously experienced ER demonstrated more internalised nuclei in mature muscle fibers, more clusters of cytoplasmic glycogen and desmin, and higher myopathic scores compared to the control group.
• However, many of the horses that had experienced ER showed signs of chronic myopathy in the microscopic analysis, although the muscle glycogen concentrations and metabolic exercise responses were normal.
• The findings suggest that an Arabian horse’s history of ER does not consistently imply a metabolic myopathy or a glycogen storage disorder.