Muscle sarcoplasmic reticulum calcium regulation in humans during consecutive days of exercise and recovery

T. A. Duhamel, R. D. Stewart, A. R. Tupling, J. Ouyang, H. J. Green
2007 Journal of applied physiology  
Duhamel TA, Stewart RD, Tupling AR, Ouyang J, Green HJ. Muscle sarcoplasmic reticulum calcium regulation in humans during consecutive days of exercise and recovery. The study investigated the hypothesis that three consecutive days of prolonged cycle exercise would result in a sustained reduction in the Ca 2ϩ -cycling properties of the vastus lateralis in the absence of changes in the sarcoplasmic (endoplasmic) reticulum Ca 2ϩ -ATPase (SERCA) protein. Tissue samples were obtained at preexercise
more » ... Pre) and postexercise (Post) on day 1 (E1) and day 3 (E3) and during recovery day 1 (R1), day 2 (R2), and day 3 (R3) in 12 active but untrained volunteers (age 19.2 Ϯ 0.27 yr; mean Ϯ SE) and analyzed for changes (nmol ⅐ mg protein Ϫ1 ⅐ min Ϫ1 ) in maximal Ca 2ϩ -ATPase activity (Vmax), Ca 2ϩ uptake and Ca 2ϩ release (phase 1 and phase 2), and SERCA isoform expression (SERCA1a and SERCA2a). At E1, reductions (P Ͻ 0.05) from Pre to Post in V max (150 Ϯ 7 vs. 121 Ϯ 7), Ca 2ϩ uptake (7.79 Ϯ 0.28 vs. 5.71 Ϯ 0.33), and both phases of Ca 2ϩ release (phase 1, 20.3 Ϯ 1.3 vs. 15.2 Ϯ 1.1; phase 2, 7.70 Ϯ 0.60 vs. 4.99 Ϯ 0.48) were found. In contrast to V max, which recovered at Pre E3 and then remained stable at Post E3 and throughout recovery, Ca 2ϩ uptake remained depressed (P Ͻ 0.05) at E3 Pre and Post and at R1 as did phase 2 of Ca 2ϩ release. Exercise resulted in an increase (P Ͻ 0.05) in SERCA1a (14% at R2) but not SERCA2a. It is concluded that rapidly adapting mechanisms protect V max following the onset of regular exercise but not Ca 2ϩ uptake and Ca 2ϩ release. short-term training; calcium-adenosinetriphosphatase; calcium uptake; calcium release; SERCA isoforms
doi:10.1152/japplphysiol.00437.2007 pmid:17656626 fatcat:qmts2uodajaahnvuvhgu4kguiy