| 15220318 |
Duhamel TA, Green HJ, Perco JG, Sandiford SD, Ouyang J: Human muscle sarcoplasmic reticulum function during submaximal exercise in normoxia and hypoxia. J Appl Physiol. 2004 Jul;97(1):180-7.
In this study, the response of the sarcoplasmic reticulum (SR) to prolonged exercise, performed in normoxia (inspired O (2) fraction = 0.21) and hypoxia (inspired O (2) fraction = 0.14) was studied in homogenates prepared from the vastus lateralis muscle in 10 untrained men (peak O (2) consumption = 3.09 +/- 0.25 l/min). In normoxia, performed at 48 +/- 2.2% peak O (2) consumption, maximal Ca (2+)-dependent ATPase activity was reduced by approximately 25% at 30 min of exercise compared with rest (168 +/- 10 vs. 126 +/- 8 micromol.g protein (-1) x min (-1)), with no further reductions observed at 90 min (129 +/- 6 micromol x g protein (-1) x min (-1)). No changes were observed in the Hill coefficient or in the Ca (2+) concentration at half-maximal activity. The reduction in maximal Ca (2+)-dependent ATPase activity at 30 min of exercise was accompanied by oxalate-dependent reductions (P < 0.05) in Ca (2+) uptake by approximately 20% (370 +/- 22 vs. 298 +/- 25 micromol x g protein (-1) x min (-1)). Ca (2+) release, induced by 4-chloro-m-cresol and assessed into fast and slow phases, was decreased (P < 0.05) by approximately 16 and approximately 32%, respectively, by 90 min of exercise. No differences were found between normoxia and hypoxia for any of the SR properties examined. It is concluded that the disturbances induced in SR Ca (2+) cycling with prolonged moderate-intensity exercise in human muscle during normoxia are not modified when the exercise is performed in hypoxia. |
1(0,0,0,1) |