• horse;
  • sarcoplasmic reticulum;
  • calcium uptake;
  • calcium-magnesium-adenosinetriphosphatase


A method has been developed for isolating equine sarcoplasmic reticulum (SR) and measuring calcium uptake by modifying methods previously established in rat and rabbit muscle tissue. Excisional biopsies were used to obtain muscle samples from the gluteal muscles of 10 Quarter Horses. Sarcoplasmic reticulum vesicles were isolated through homogenisation and differential centrifugation. Calcium uptake into the vesicles was monitored spectrophotometrically using a calcium probe, antipyrylazo III. An enzyme linked optical assay was employed to assess Mg++ -stimulated, Ca++ -stimulated and total ATPase activity in the isolated SR vesicles. The present results provide a system for obtaining SR microsomes and measuring calcium uptake in the isolated vesicles in a relatively short period of time. High intensity sprinting decreased calcium uptake and Ca-ATPase activity of SR vesicles in horses.