Paradoxical effects of prior activity on human sarcoplasmic reticulum Ca2+-ATPase response to exercise

• Published in: Journal of applied physiology (1985) 2003-07, Vol.95 (1), p.138-144
• Main Authors: Tupling, A. R, Green, H. J, Roy, B. D, Grant, S, Ouyang, J
• Format: Article
• Language: English
• Subjects: Adult; Anaerobic Threshold - physiology; Biological and medical sciences; Blotting, Western; Calcium - metabolism; Calcium-Transporting ATPases - metabolism; Electrophoresis, Polyacrylamide Gel; Exercise; Exercise - physiology; Exercise Test; Female; Fundamental and applied biological sciences. Psychology; Humans; Isoenzymes - metabolism; Kinetics; Male; Muscle Fatigue - physiology; Muscle, Skeletal - enzymology; Muscle, Skeletal - physiology; Muscular system; Proteins; Pulmonary Gas Exchange - physiology; Sarcoplasmic Reticulum - enzymology; Sarcoplasmic Reticulum - physiology; Sarcoplasmic Reticulum Calcium-Transporting ATPases; Striated muscle. Tendons; Vertebrates: osteoarticular system, musculoskeletal system
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00483.2002

Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 Submitted 31 May 2002 ; accepted in final form 26 March 2003 To investigate the effects of intermittent heavy exercise (HE) on sarcoplasmic reticulum (SR) maximal Ca 2+ -ATPase activity ( V max ) and Ca 2+ uptake, a continuous two-stage standardized cycling test was performed before and after HE by untrained men [peak aerobic power ( O 2 peak ) = 42.9 ± 2.7 ml · kg -1 · min -1 ]. The HE consisted of 16 bouts of cycling performed for 6 min each hour at 90% O 2 peak . Tissue was obtained from the vastus lateralis by needle biopsy before and during each cycle test. Before HE, reductions ( P < 0.05; µmol · g protein -1 · min -1 ) of 16 and 31% were observed in V max and Ca 2+ uptake, respectively, after 40 min of the standardized test. Resting V max and Ca 2+ uptake were depressed ( P < 0.05) by 19 and 30%, respectively, when measured 36–48 h after HE. During the standardized test, after HE, V max increased ( P < 0.05) by 20%, whereas no change was observed in Ca 2+ uptake. The HE protocol resulted in small increases ( P < 0.05) and decreases ( P < 0.05) in sarco(endo)plasmic reticulum Ca 2+ -ATPase (SERCA) 2a and SERCA1 expression, respectively, as determined by Western blotting techniques. These results indicate that SR Ca 2+ -sequestering function in response to a prolonged exercise test depends on prior activity status, such that rested muscles exhibit a decrease and prior exercised muscles, an increase in Ca 2+ -ATPase activity. Moreover, it appears that changes in SERCA content can occur in response to a sustained session of intermittent exercise. Ca 2+ sequestering; continuous exercise; fatigue; vastus lateralis; SERCA isoforms Address for reprint requests and other correspondence: H. J. Green, Dept. of Kinesiology, Univ. of Waterloo, Waterloo, ON, Canada N2L 3G1 (E-mail: green{at}healthy.uwaterloo.ca ).