Exercise-induced changes in the activities of beta-glucuronidase and N-acetyl-beta-D-glucosaminidase in plasma and muscle of standardbred trotters.

This study investigates the changes in activities of certain enzymes in the blood and muscle of racing horses before and after exercise. The findings indicate that while the enzyme activity does increase after exercise, these changes primarily reflect an increase in certain white blood cells, making them poor indicators of exercise-induced muscle damage.

Investigation of Lysosomal Enzymes

• The research focuses on two particular lysosomal enzymes: beta-glucuronidase and N-acetyl-beta-D-glucosaminidase. In the past, these enzymes have been observed to increase activity in the muscles after endurance exercise.
• The main objective of the study was to investigate whether there were measurable activities of these lysosomal enzymes in horse plasma (the liquid part of the blood) and whether any changes in muscle following exercise are mirrored in the plasma.

Exercise and Sample Collection

• Six trained Standardbred trotters were made to perform three bouts of exercise with a 1-hour interval between each session. This process was repeated three days later.
• Blood samples were drawn from the horses and muscle biopsies taken from the middle gluteal muscle, both before and after the exercise.

Enzyme Activity Measurement

• The activities of beta-glucuronidase and N-acetyl-beta-D-glucosaminidase were measured in both plasma and muscle specimens.
• The activity of N-acetyl-beta-D-glucosaminidase in plasma increased immediately after exercise but returned to base level within 4 hours.
• The activity of the same enzyme in muscle and the activity of beta-glucuronidase in muscle and plasma, however, increased 2 days after exercise and returned to base level on day 3.

Reflection of Phagocytes Infiltration

• The pattern of enzyme activity correlated with the DNA content in muscle. This indicates that the pattern of enzyme activity reflected the infiltration of phagocytes (types of white blood cells) into the muscle tissue that was injured during exercise.
• The researchers concluded that the activities of the lysosomal enzymes in the plasma do increase after exercise and that these changes are primarily due to an increase in the number of neutrophils (type of phagocyte).

Significance of Findings

• Gauging by these observations, it can be determined that the plasma activities of these particular lysosomal enzymes are not indicative of exercise-induced muscle damage,contrary to what might be expected.