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J Appl Physiol (January 17, 2008). doi:10.1152/japplphysiol.01151.2007
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Submitted on October 26, 2007
Accepted on January 11, 2008

Acute Responses in Muscle Mitochondrial and Cytosolic Enzyme Activities During Heavy Internittent Exercise

H. J. Green1*, Eric B. Bombardier2, T. A. Duhamel3, Graham Paul Holloway4, A. Russell Tupling5, and J. Ouyang6

1 Department of Kinesiology, University of Waterloo, Waterloo, Canada
2 Kinesiology, University of Waterloo, Canada
3 St.Boniface General Hospital Research Centre, University of Manitoba, Winnipeg, Canada
4 Human Health and Nutritional Sciences, University of Guelph, Guelph, Canada; , Canada
5 Kinesiology, University of Waterloo, Waterloo, Canada
6 University of Waterloo, United States

* To whom correspondence should be addressed. E-mail: green{at}healthy.uwaterloo.ca.

To examine the effects of repetitive bouts of heavy exercise on the maximal activities of enzymes representative of the major metabolic pathways and segments, 13 untrained volunteers (VO2peak=44.3±2.3 ml.kg-1. min-1) cycled at ~ 91% for 6 min once per h for 16 h. Maximal enzyme activities (Vmax, mol.kg-1 protein .h-1) were measured in homogenates from tissue extracted from the vastus lateralis before (B) and after (A) exercise at repetitions 1 (R1), 2 (R2), 9 (R9) and 16 (R16). For the mitochondrial enzymes, exercise resulted in reductions (P<0.05) in cytochrome oxidase (COX, 14.6 %), near significant reductions in malate dehydrogenase (4.06% ; P=0.06) and succinic dehydrogenase (4.82 % ;p=0.09), near significant increases in {beta}-hydroxyacyl CoA dehydrogenase (4.94 %; P=0.08) and no change in citrate synthase (CS, 2.88 %; P=0.37). For the cytosolic enzymes, exercise reduced (P<0.05) Vmax in hexokinase (HEX, 4.4 %), creatine phosphokinase (9.0 %), total phosphorylase ( 13.5 %), phosphofructokinase ( 16.6 %), pyruvate kinase (PK, 14.1 %) and lactate dehydrogenase (10.7%). Repetition-dependent reductions (P<0.05) in Vmax were observed for CS ( 1R,2R>16R), COX ( R1,R2>R16), HEX (1R,2R>16R) and PK (R9>16R). It is concluded that heavy exercise results in transient reductions in a wide range of enzymes involved in different metabolic functions and that in the case of selected enzymes, multiple repetitions of the exercise reduce average Vmax.




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Am. J. Physiol. Regul. Integr. Comp. Physiol.Home page
H. J. Green, E. Bombardier, T. A. Duhamel, R. D. Stewart, A. R. Tupling, and J. Ouyang
Metabolic, enzymatic, and transporter responses in human muscle during three consecutive days of exercise and recovery
Am J Physiol Regulatory Integrative Comp Physiol, October 1, 2008; 295(4): R1238 - R1250.
[Abstract] [Full Text] [PDF]




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