Dissociation between changes in muscle Na+-K+-ATPase isoform abundance and activity with consecutive days of exercise and recovery.
The early plasticity of vastus lateralis Na(+)-K(+)-ATPase to the abrupt onset of prolonged submaximal cycling was studied in 12 untrained participants (Vo(2 peak) 44.8 +/- 2.0 ml x kg(-1) x min(-1), mean +/- SE) using a 6-day protocol (3 days of exercise plus 3 days of recovery). Tissue samples were extracted prior to (Pre) and following exercise (Post) on day 1 (E1) and day 3 (E3) and on each day of recovery (R1, R2, R3) and analyzed for changes in maximal protein (beta(max)) (vanadate-facilitated [(3)H]ouabain binding), alpha- and beta-isoform concentration (quantitative immunoblotting) and maximal Na(+)-K(+)-ATPase activity (V(max)) (3-O-methylfluorescein K(+)-stimulated phosphatase assay). For beta(max) (pmol/g wet wt), an increase (P < 0.05) of 11.8% was observed at R1 compared with E1-Pre (340 +/- 14 vs 304 +/- 17). For the alpha-isoforms alpha(1), alpha(2), and alpha(3), increases (P < 0.05) of 46, 42, and 31% were observed at R1, respectively. For the beta-isoform, beta(1) and beta(2) increased (P < 0.05) by 19 and 28% at R1, whereas beta(3) increased (P < 0.05) by 18% at R2. With the exception of alpha(2) and alpha(3), the increases in the isoforms persisted at R3. Exercise resulted in an average decrease (P < 0.05) in V(max) by 14.3%. No differences were observed in V(max) at E1 - Pre and E3 - Pre or between R1, R2, and R3. It is concluded that 3 days of prolonged exercise is a powerful stimulus for the rapid upregulation of the Na(+)-K(+)-ATPase subunit isoforms. Contrary to our hypothesis, the increase in subunit expression is not accompanied by increases in the maximal catalytic activity.
Green
H J
HJ
Department of Kinesiology, University of Waterloo, Waterloo, ON, Canada, N2L 3G1. green@healthy.uwaterloo.ca
Duhamel
T A
TA
Stewart
R D
RD
Tupling
A R
AR
Ouyang
J
J
D000222:Adaptation, Physiological / Q000502:physiology*; D000328:Adult; D002950:Citrate (si)-Synthase / Q000378:metabolism; D004789:Enzyme Activation / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism*; D008297:Male; D018482:Muscle, Skeletal / Q000201:enzymology*; D010101:Oxygen Consumption / Q000502:physiology; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013997:Time Factors
D007527:Isoenzymes; D002950:Citrate (si)-Synthase; D000254:Sodium-Potassium-Exchanging ATPase