title: Exercise-induced changes in the activities of beta-glucuronidase and N-acetyl-beta-D-glucosaminidase in plasma and muscle of standardbred trotters.
abstract: The activities of lysosomal enzymes, such as beta-glucuronidase and N-acetyl-beta-D-glucosaminidase, have been shown to increase in muscle after endurance exercise. We examined whether measurable activities of lysosomal enzymes are present in equine plasma and whether the exercise-induced changes in the muscle are reflected in plasma. Six trained Standardbred trotters performed three exercise bouts with 1 h intervals and the same procedure was repeated 3 days later. Venous blood samples and muscle biopsies from the middle gluteal muscle were taken before and after exercise. The activities of beta-glucuronidase and N-acetyl-beta-D-glucosaminidase were measured both from plasma and muscle specimens. Cell infiltration into the muscle after exercise was evaluated by the DNA content and histochemically by haematoxylin stain. The activity of N-acetyl-beta-D-glucosaminidase in plasma was increased immediately after exercise, but had returned to the basal level at 4 h. N-acetyl-beta-D-glucosaminidase in muscle and beta-glucuronidase in muscle and plasma increased 2 days after exercise and returned to the basal level on day 3. A similar pattern was seen when the exercise protocol was repeated 3 days later, except that the activities continued to increase during the 3 days after exercise. The DNA content in muscle correlated with beta-glucuronidase in muscle and plasma and with the N-acetyl-beta-D-glucosaminidase in muscle indicating that the activities reflect the infiltration of phagocytes into the exercise-injured muscle. It can be concluded that the activities of the lysosomal enzymes in plasma increase after exercise and that the changes are mainly due to a simultaneous increase in the number of neutrophils. Therefore, plasma activities of the lysosomal enzymes are poor indicators of exercise-induced muscle damage.
authors.affiliation: Department of Basic Veterinary Sciences, University of Helsinki, Finland.
authors.forename: S M
authors.initials: SM
authors.lastname: Raulo
authors.forename: S
authors.initials: S
authors.lastname: Hyyppa
authors.forename: L A
authors.initials: LA
authors.lastname: Räsänen
authors.forename: A R
authors.initials: AR
authors.lastname: Pösö
mesh_terms: D000118:Acetylglucosaminidase / Q000097:blood / Q000378:metabolism*; D000818:Animals; D001706:Biopsy / Q000662:veterinary; D004247:DNA / Q000032:analysis; D005260:Female; D005966:Glucuronidase / Q000097:blood / Q000378:metabolism*; D006736:Horses / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000737:chemistry / Q000201:enzymology*; D010805:Physical Conditioning, Animal / Q000502:physiology*
chemical_list: D004247:DNA; D005966:Glucuronidase; D000118:Acetylglucosaminidase