title: Downregulation in muscle Na(+)-K(+)-ATPase following a 21-day expedition to 6,194 m.
abstract: To investigate the hypothesis that acclimatization to altitude would result in a downregulation in muscle Na(+)-K(+)-ATPase pump concentration, tissue samples were obtained from the vastus lateralis muscle of six volunteers (5 males and 1 female), ranging in age from 24 to 35 yr, both before and within 3 days after a 21-day expedition to the summit of Mount Denali, Alaska (6,194 m). Na(+)-K(+)-ATPase, measured by the [(3)H]ouabain-binding technique, decreased by 13.8% [348 +/- 12 vs. 300 +/- 7.6 (SE) pmol/g wet wt; P < 0.05]. No changes were found in the maximal activities (mol. kg protein(-1). h(-1)) of the mitochondrial enzymes, succinic dehydrogenase (3.63 +/- 0.20 vs. 3.25 +/- 0.23), citrate synthase (4. 76 +/- 0.44 vs. 4.94 +/- 0.44), and malate dehydrogenase (12.6 +/- 1. 8 vs. 12.7 +/- 1.2). Similarly, the expedition had no effect on any of the histochemical properties examined, namely fiber-type distribution (types I, IIA, IIB, IC, IIC, IIAB), area, capillarization, and succinic dehydrogenase activity. Peak aerobic power (52.3 +/- 2.1 vs. 50.6 +/- 1.9 ml. kg(-1). min(-1)) and body mass (76.9 +/- 3.7 vs. 75.5 +/- 2.9 kg) were also unaffected. We concluded that acclimatization to altitude results in a downregulation in muscle Na(+)-K(+)-ATPase pump concentration, which occurs without changes in oxidative potential and other fiber-type histochemical properties.
authors.affiliation: Department of Kinesiology, University of Waterloo, Waterloo N2L3G1, Ontario K1Y4E9.
authors.forename: H
authors.initials: H
authors.lastname: Green
authors.forename: B
authors.initials: B
authors.lastname: Roy
authors.forename: S
authors.initials: S
authors.lastname: Grant
authors.forename: M
authors.initials: M
authors.lastname: Burnett
authors.forename: R
authors.initials: R
authors.lastname: Tupling
authors.forename: C
authors.initials: C
authors.lastname: Otto
authors.forename: A
authors.initials: A
authors.lastname: Pipe
authors.forename: D
authors.initials: D
authors.lastname: McKenzie
mesh_terms: D015094:3-Hydroxyacyl CoA Dehydrogenases / Q000378:metabolism; D000064:Acclimatization / Q000502:physiology*; D000328:Adult; D000531:Altitude; D001835:Body Weight; D002950:Citrate (si)-Synthase / Q000378:metabolism; D015536:Down-Regulation; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008291:Malate Dehydrogenase / Q000378:metabolism; D008297:Male; D009051:Mountaineering; D018482:Muscle, Skeletal / Q000201:enzymology*; D010101:Oxygen Consumption / Q000502:physiology; D012123:Pulmonary Ventilation / Q000502:physiology; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013385:Succinate Dehydrogenase / Q000378:metabolism; D013997:Time Factors
chemical_list: D015094:3-Hydroxyacyl CoA Dehydrogenases; D007770:L-Lactate Dehydrogenase; D008291:Malate Dehydrogenase; D013385:Succinate Dehydrogenase; D002950:Citrate (si)-Synthase; D000254:Sodium-Potassium-Exchanging ATPase