title: Importance of pH regulation and lactate/H+ transport capacity for work production during supramaximal exercise in humans.
abstract: We examine the influence of the cytosolic and membrane-bound contents of carbonic anhydrase (CA; CAII, CAIII, CAIV, and CAXIV) and the muscle content of proteins involved in lactate and proton transport [monocarboxylate transporter (MCT) 1, MCT4, and Na(+)/H(+) exchanger 1 (NHE1)] on work capacity during supramaximal exercise. Eight healthy, sedentary subjects performed exercises at 120% of the work rate corresponding to maximal oxygen uptake (W(max)) until exhaustion in placebo (Con) and metabolic alkalosis (Alk) conditions. The total (W(tot)) and supramaximal work performed (W(sup)) was measured. Muscle biopsies were obtained before and immediately after standardized exercises (se) at 120% W(max) in both conditions to determine the content of the targeted proteins, the decrease in muscle pH (DeltapH(m)), and the muscle lactate accumulation ([Lac](m)) per joule of W(sup) (DeltapH(m)/W(sup-se) and Delta[Lac](m)/W(sup-se), respectively) and the dynamic buffer capacity. In Con, W(sup) was positively [corrected] correlated with [corrected] MCT1, and tended to be positively correlated with MCT4 and NHE1. CAII + CAIII were correlated positively with DeltapH(m)/W(sup-se) and negatively with Delta[Lac](m)/W(sup-se), while CAIV was positively related to W(tot). The changes in W(sup) with Alk were correlated positively with those in dynamic buffer capacity and negatively with W(sup) in Con. Performance improvement with Alk was greater in subjects having a low content of proteins involved in pH regulation and lactate/proton transport. These results show the importance of pH regulating mechanisms and lactate/proton transport on work capacity and the role of the CA to delay decrease in pH(m) and accumulation in [Lac](m) during supramaximal exercise in humans.
authors.affiliation: Equipe Modélisation des Activités Sportives, Département STAPS, Université de Savoie, Campus Universitaire, F-73376 Le Bourget du Lac Cedex, France. laurent.messonnier@univ-savoie.fr
authors.forename: Laurent
authors.initials: L
authors.lastname: Messonnier
authors.forename: Michael
authors.initials: M
authors.lastname: Kristensen
authors.forename: Carsten
authors.initials: C
authors.lastname: Juel
authors.forename: Christian
authors.initials: C
authors.lastname: Denis
mesh_terms: D000328:Adult; D000471:Alkalosis / Q000201:enzymology / Q000378:metabolism* / Q000503:physiopathology; D002256:Carbonic Anhydrases / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000378:metabolism; D015444:Exercise; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000378:metabolism; D019344:Lactic Acid / Q000378:metabolism*; D016014:Linear Models; D008297:Male; D026901:Membrane Transport Proteins / Q000378:metabolism*; D027501:Monocarboxylic Acid Transporters / Q000378:metabolism; D009119:Muscle Contraction; D018763:Muscle Fatigue; D009124:Muscle Proteins / Q000378:metabolism; D018482:Muscle, Skeletal / Q000201:enzymology / Q000378:metabolism*; D010101:Oxygen Consumption; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism; D027981:Symporters / Q000378:metabolism; D000099233:Monocarboxylate Transport Protein 1
chemical_list: D002256:Carbonic Anhydrases; D027682:Cation Transport Proteins; D007527:Isoenzymes; D019344:Lactic Acid; D026901:Membrane Transport Proteins; D027501:Monocarboxylic Acid Transporters; D009124:Muscle Proteins; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers; D027981:Symporters; D000099233:Monocarboxylate Transport Protein 1; C406962:SLC16A4 protein, human; C490998:SLC9A1 protein, human