Effects of a 21-day expedition to 6,194 m on human skeletal muscle SR Ca2+-ATPase.
We investigated the effects of a 21-day expedition to the summit of Mount Denali, Alaska (6,194 m) on selected Ca2+ sequestration properties of sarcoplasmic reticulum (SR) calcium pump in vastus lateralis muscle. Muscle samples were obtained by biopsy from 5 male climbers (peak oxygen consumption, VO2peak = 52.3 +/- 2.1 mL.kg(-1).min(-1)) approximately 7 days prior to (PRE) and 4 days following (POST) the expedition. A comparison of PRE versus POST measures of maximal Ca2+-ATPase activities (117 +/- 8.5 vs. 97.6 +/- 5.6 nmol.mg protein(-1).min(-1)) and Ca2+-uptake (204 +/- 15 vs. 161 +/- 11 nmol.mg protein(-1).min(-1)) measured in crude homogenates obtained from pre-exercised muscle, indicated only an effect (p < 0.05) of the expedition on Ca2+-uptake. The reduction in Ca2+-ATPase activity, representing 16.6%, was not significant (p = 0.089). The sarco endoplasmic reticulum calcium (SERCA)-ATPase isoforms, measured using Western blotting techniques, revealed a small reduction (p < 0.05) in SERCA 1 (-4.6 +/- 1.9%), but not in SERCA 2a (+2.0 +/- 1.4%). Prior to the expedition, both Ca2+-ATPase activity and Ca2+-uptake were reduced (p < 0.05) by approximately 34 and 18%, respectively, following 40 min of a two-step continuous cycling task (20 min at 59% VO2peak and 20 min at 74% VO2peak). The exercise-induced reduction in Ca2+-ATPase activity was independent of fiber type. Only in the case of Ca2+-uptake was a lower exercise response (p < 0.05) observed following the expedition, an effect that was due to the lower resting value. It is concluded that acclimatization as experienced during a mountaineering expedition induces changes in the properties of the SR Ca2+-pump, and particularly to Ca2+-sequestering function.
Green
H
H
Department of Kinesiology, University of Waterloo, Ont, Canada. green@healthy.uwaterloo.ca
Roy
B
B
Grant
S
S
Tupling
R
R
Otto
C
C
Pipe
A
A
McKenzie
D
D
Ouyang
J
J
D000064:Acclimatization / Q000502:physiology; D000328:Adult; D000531:Altitude; D001706:Biopsy; D015153:Blotting, Western; D000252:Calcium-Transporting ATPases / Q000032:analysis* / Q000378:metabolism; D004734:Energy Metabolism / Q000502:physiology; D015444:Exercise / Q000502:physiology; D005080:Exercise Test; D005101:Expeditions; D005260:Female; D006801:Humans; D008297:Male; D009051:Mountaineering; D018482:Muscle, Skeletal / Q000378:metabolism; D010101:Oxygen Consumption; D012146:Rest / Q000502:physiology; D012519:Sarcoplasmic Reticulum / Q000737:chemistry* / Q000378:metabolism; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D013997:Time Factors
D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000252:Calcium-Transporting ATPases