title: Altered sarcoplasmic reticulum function after high-intensity exercise.
abstract: This study examined the effects of acute high-intensity exercise on the rate and capacity of Ca2+ uptake and Ca2+-stimulated adenosinetriphosphatase (ATPase) activity of the sarcoplasmic reticulum and the reversibility of these effects. Thoroughbred horses were run at maximal O2 uptake on a high-speed treadmill until fatigued. Muscle temperatures and biopsy samples were collected at rest, immediately after exercise, and 30 and 60 min after exercise. Blood samples were collected at rest and 5 min after exercise. Muscle and blood (lactate concentration) were three- and fivefold greater than pre-exercise values. Muscle temperature and pH immediately after post-exercise were 43 degrees C and 6.55, respectively, but approached rest values by 60 min after exercise. The initial rate and maximal capacity of Ca2+ uptake of muscle homogenates and isolated sarcoplasmic reticulum were significantly depressed immediately after exercise. This depression was paralleled by decreased activity of the Ca2+-stimulated ATPase. However, both Ca2+ uptake (rate and capacity) and Ca2+4-ATPase activity had returned to normal by 60 min after exercise. These findings demonstrate that changes in sarcoplasmic reticulum function after high-intensity exercise may be induced but not sustained by local changes in muscle pH and/or temperature.
authors.affiliation: Department of Veterinary and Comparative Anatomy, College of Veterinary Medicine, Washington State University, Pullman 99164-6520.
authors.forename: S K
authors.initials: SK
authors.lastname: Byrd
authors.forename: L J
authors.initials: LJ
authors.lastname: McCutcheon
authors.forename: D R
authors.initials: DR
authors.lastname: Hodgson
authors.forename: P D
authors.initials: PD
authors.lastname: Gollnick
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001831:Body Temperature; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism*; D002118:Calcium / Q000097:blood / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D005260:Female; D006736:Horses; D006863:Hydrogen-Ion Concentration; D008297:Male; D009132:Muscles / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology; D005082:Physical Exertion / Q000502:physiology*; D012519:Sarcoplasmic Reticulum / Q000502:physiology*
chemical_list: D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D002118:Calcium