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Impaired muscle Ca2+ and K+ regulation contribute to poor exercise performance post-lung transplantation
journal contribution
posted on 2003-10-01, 00:00 authored by M McKenna, Steve FraserSteve Fraser, J Li, X Wang, M Carey, E Side, J Morton, G Snell, K Kjeldsen, T WilliamsLung transplant recipients (LTx) exhibit marked peripheral limitations to exercise. We investigated whether skeletal muscle Ca2+ and K+ regulation might be abnormal in eight LTx and eight healthy controls. Peak oxygen consumption and arterialized venous plasma [K+] (where brackets denote concentration) were measured during incremental exercise. Vastus lateralis muscle was biopsied at rest and analyzed for sarcoplasmic reticulum Ca2+ release, Ca2+ uptake, and Ca2+-ATPase activity rates; fiber composition; Na+-K+-ATPase (K+-stimulated 3-O-methylfluorescein phosphatase) activity and content ([3H]ouabain binding sites); as well as for [H+] and H+-buffering capacity. Peak oxygen consumption was 47% less in LTx (P < 0.05). LTx had lower Ca2+ release (34%), Ca2+ uptake (31%), and Ca2+-ATPase activity (25%) than controls (P < 0.05), despite their higher type II fiber proportion (LTx, 75.0 ± 5.8%; controls, 43.5 ± 2.1%). Muscle [H+] was elevated in LTx (P < 0.01), but buffering capacity was similar to controls. Muscle 3-O-methylfluorescein phosphatase activity was 31% higher in LTx (P < 0.05), but [3H]ouabain binding content did not differ significantly. However, during exercise, the rise in plasma [K+]-to-work ratio was 2.6-fold greater in LTx (P < 0.05), indicating impaired K+ regulation. Thus grossly subnormal muscle calcium regulation, with impaired potassium regulation, may contribute to poor muscular performance in LTx.
History
Journal
Journal of applied physiologyVolume
95Issue
4Pagination
1606 - 1616Publisher
American Physiological SocietyLocation
Bethesda, Md.ISSN
8750-7587eISSN
1522-1601Language
engPublication classification
C1.1 Refereed article in a scholarly journalUsage metrics
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Science & TechnologyLife Sciences & BiomedicinePhysiologySport Sciencescalcium releasecalcium adenosine 5 '-triphosphataseNa+-K+ pumpmuscle fiber typerespiratory diseaseHUMAN SKELETAL-MUSCLEOBSTRUCTIVE PULMONARY-DISEASESARCOPLASMIC-RETICULUMOXIDATIVE CAPACITYATPASE ACTIVITYFAST-TWITCHFATIGUEFIBERSPOTASSIUMHEART
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