Sarcoplasmic Reticulum Ca2+-ATPase Activity and Glycogen Content
in Various Fiber Types after Intensive Exercise in Thoroughbred Horses |
| |
| Authors: | Yoshio MINAMI Seiko YAMANO Minako KAWAI Atsushi HIRAGA Hirofumi MIYATA |
| |
| Institution: | 1. Biological Sciences, Graduate School of Medicine, Yamaguchi University, Yoshida 1677–1, Yamaguchi 753-8515, Japan;2. Science Research Center, Yamaguchi University, Yoshida 1677–1, Yamaguchi 753-8511, Japan;3. Equine Research Institute, Japan Racing Association, 321–4 Tokami-cho, Utsunomiya, Tochigi 320-0856, Japan |
| |
| Abstract: | To find a new parameter indicating muscle fitness in Thoroughbred horses, we examined
time-dependent recovery of glycogen content and sarcoplasmic reticulum (SR)
Ca2+-ATPase activity of skeletal muscle after intensive treadmill running.
Two repeated 50-sec running sessions (13 m/sec) were performed on a flat treadmill
(approximately 90%VO2max). Muscle samples of the middle gluteal muscle were
taken before exercise (pre) and 1 min, 20 min, 60 min, and 24 hr after exercise. Muscle
fiber type composition was determined in the pre muscle samples by immunohistochemical
staining with monoclonal antibody to myosin heavy chain. SR Ca2+-ATPase
activity of the muscle and glycogen content of each muscle fiber type were determined with
biochemical analysis and quantitative histochemical staining, respectively. As compared to
the pre value, the glycogen content of each muscle fiber type was reduced by 15–27% at 1
min, 20 min, and 60 min after the exercise and recovered to the pre value at 24 hr after
exercise test. These results indicate that 24 hr is enough time to recover glycogen
content after short-term intensive exercise. The mean value of the SR
Ca2+-ATPase activity showed a slight decrease (not significant) immediately
after exercise, and complete recovery at 60 min after exercise. There were no significant
relationship between the changes in glycogen content of each muscle fiber type and SR
Ca2+-ATPase. Although further studies are needed, SR Ca2+-ATPase
is not a useful parameter to detect muscle fitness, at least in Thoroughbred horses. |
| |
| Keywords: | glycogen recovery sarcoplasmic reticulum Ca2+-ATPase Thoroughbred |
|
|
