Paradoxical effects of prior activity on human sarcoplasmic reticulum Ca2+-ATPase response to exercise.
To investigate the effects of intermittent heavy exercise (HE) on sarcoplasmic reticulum (SR) maximal Ca2+-ATPase activity (Vmax) and Ca2+ uptake, a continuous two-stage standardized cycling test was performed before and after HE by untrained men [peak aerobic power (Vo -->Vo2 peak) = 42.9 +/- 2.7 ml. kg-1 x min-1]. The HE consisted of 16 bouts of cycling performed for 6 min each hour at 90% Vo2 peak. Tissue was obtained from the vastus lateralis by needle biopsy before and during each cycle test. Before HE, reductions (P < 0.05 micromol. g protein-1x min-1) of 16 and 31% were observed in Vmax and Ca2+ uptake, respectively, after 40 min of the standardized test. Resting Vmax and Ca2+ uptake were depressed (P < 0.05) by 19 and 30%, respectively, when measured 36-48 h after HE. During the standardized test, after HE, Vmax increased (P < 0.05) by 20%, whereas no change was observed in Ca2+ uptake. The HE protocol resulted in small increases (P < 0.05) and decreases (P < 0.05) in sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) 2a and SERCA1 expression, respectively, as determined by Western blotting techniques. These results indicate that SR Ca2+-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 Ca2+-ATPase activity. Moreover, it appears that changes in SERCA content can occur in response to a sustained session of intermittent exercise.
Tupling
A R
AR
Department of Kinesiology, University of Waterloo, Ontario, Canada N2L 3G1.
Green
H J
HJ
Roy
B D
BD
Grant
S
S
Ouyang
J
J
D000328:Adult; D015308:Anaerobic Threshold / Q000502:physiology; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D007700:Kinetics; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology; D018482:Muscle, Skeletal / Q000201:enzymology* / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012519:Sarcoplasmic Reticulum / Q000201:enzymology* / Q000502:physiology*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases
D007527:Isoenzymes; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; C506943:ATP2A1 protein, human; D000252:Calcium-Transporting ATPases; D002118:Calcium