Effects of endurance training status and sex differences on Na+,K+-pump mRNA expression, content and maximal activity in human skeletal muscle.
OBJECTIVE
This study investigated the effects of endurance training status and sex differences on skeletal muscle Na+,K+-pump mRNA expression, content and activity.


METHODS
Forty-five endurance-trained males (ETM), 11 recreationally active males (RAM), and nine recreationally active females (RAF) underwent a vastus lateralis muscle biopsy. Muscle was analysed for Na+,K+-pump alpha1, alpha2, alpha3, beta1, beta2 and beta3 isoform mRNA expression (real-time reverse transcription-polymerase chain reaction), content ([3H]-ouabain-binding site) and maximal activity (3-O-methylfluorescein phosphatase, 3-O-MFPase).


RESULTS
ETM demonstrated lower alpha1, alpha3, beta2 and beta3 mRNA expression by 74%, 62%, 70% and 82%, respectively, than RAM (P<0.04). In contrast, [3H]-ouabain binding and 3-O-MFPase activity were each higher in ETM than in RAM, by 16% (P<0.03). RAM demonstrated a 230% and 364% higher alpha3 and beta3 mRNA expression than RAF, respectively (P<0.05), but no significant sex differences were found for alpha1, alpha2, beta1 or beta2 mRNA, [3H]-ouabain binding or 3-O-MFPase activity. No significant correlation was found between years of endurance training and either [3H]-ouabain binding or 3-O-MFPase activity. Significant but weak correlations were found between the number of training hours per week and 3-O-MFPase activity (r=0.31, P<0.02) and between incremental exercise VO2(peak)) and both [3H]-ouabain binding (r=0.33, P<0.01) and 3-O-MFPase activity (r=0.28, P<0.03).


CONCLUSIONS
Isoform-specific differences in Na+,K+-pump mRNA expression were found with both training status and sex differences, but only training status influenced Na+,K+-pump content and maximal activity in human skeletal muscle.
Murphy
K T
KT
Muscle, Ions and Exercise Group, School of Human Movement, Recreation and Performance, Centre for Ageing, Rehabilitation, Exercise and Sport Science (CARES), Victoria University, Melbourne, Vic., Australia.
Aughey
R J
RJ
Petersen
A C
AC
Clark
S A
SA
Goodman
C
C
Hawley
J A
JA
Cameron-Smith
D
D
Snow
R J
RJ
McKenna
M J
MJ
D000328:Adult; D000704:Analysis of Variance; D001665:Binding Sites; D001706:Biopsy; D003430:Cross-Sectional Studies; D021983:Cyclophilins / Q000235:genetics; D004789:Enzyme Activation; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000201:enzymology*; D010042:Ouabain / Q000378:metabolism; D010806:Physical Education and Training; D010807:Physical Endurance; D020033:Protein Isoforms / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012737:Sex Factors; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis / Q000235:genetics*; D013997:Time Factors
D020033:Protein Isoforms; D012333:RNA, Messenger; D010042:Ouabain; C045349:3-O-methyl-fluorescein phosphatase; D021983:Cyclophilins; D000254:Sodium-Potassium-Exchanging ATPase