title: Acute responses in muscle mitochondrial and cytosolic enzyme activities during heavy intermittent exercise.
abstract: 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 [peak aerobic power (Vo(2 peak)) = 44.3 +/- 2.3 ml.kg(-1).min(-1)] cycled at approximately 91% Vo(2 peak) for 6 min once per hour for 16 h. Maximal enzyme activities (V(max), mol.kg(-1).protein.h(-1)) were measured in homogenates from tissue extracted from the vastus lateralis before and after 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-c 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) V(max) 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 V(max) were observed for CS (R1, R2 > R16), COX (R1, R2 > R16), Hex (1R, 2R > R16), and PK (R9 > R16). 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 V(max).
authors.affiliation: Dept. of Kinesiology, Univ. of Waterloo, Waterloo, ON, Canada. green@healthy.uwaterloo.ca
authors.forename: H J
authors.initials: HJ
authors.lastname: Green
authors.forename: E B
authors.initials: EB
authors.lastname: Bombardier
authors.forename: T A
authors.initials: TA
authors.lastname: Duhamel
authors.forename: G P
authors.initials: GP
authors.lastname: Holloway
authors.forename: A R
authors.initials: AR
authors.lastname: Tupling
authors.forename: J
authors.initials: J
authors.lastname: Ouyang
mesh_terms: D000328:Adult; D001642:Bicycling; D001786:Blood Glucose / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D003402:Creatine Kinase / Q000378:metabolism; D003600:Cytosol / Q000201:enzymology*; D003576:Electron Transport Complex IV / Q000378:metabolism; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D006003:Glycogen / Q000096:biosynthesis; D006801:Humans; D006903:Hydroxymethylglutaryl CoA Reductases / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D007785:Lactose / Q000378:metabolism; D008291:Malate Dehydrogenase / Q000378:metabolism; D008297:Male; D008931:Mitochondria, Muscle / Q000201:enzymology*; D027501:Monocarboxylic Acid Transporters / Q000378:metabolism; D025221:Phosphofructokinases / Q000378:metabolism; D010766:Phosphorylation; D011770:Pyruvate Kinase / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013385:Succinate Dehydrogenase / Q000378:metabolism
chemical_list: D001786:Blood Glucose; D027501:Monocarboxylic Acid Transporters; D006003:Glycogen; D006903:Hydroxymethylglutaryl CoA Reductases; D007770:L-Lactate Dehydrogenase; D008291:Malate Dehydrogenase; D013385:Succinate Dehydrogenase; D003576:Electron Transport Complex IV; D025221:Phosphofructokinases; D011770:Pyruvate Kinase; D003402:Creatine Kinase; D000254:Sodium-Potassium-Exchanging ATPase; D007785:Lactose; D002118:Calcium