AUTHOR=Maciejewski Hugo , Bourdin Muriel , Féasson Léonard , Dubouchaud Hervé , Denis Christian , Freund Hubert , Messonnier Laurent A. 

TITLE=Muscle MCT4 Content Is Correlated with the Lactate Removal Ability during Recovery Following All-Out Supramaximal Exercise in Highly-Trained Rowers

JOURNAL=Frontiers in Physiology

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2016.00223

DOI=10.3389/fphys.2016.00223

ISSN=1664-042X

ABSTRACT=<p>The purpose of this study was to test if the lactate exchange (γ<sub>1</sub>) and removal (γ<sub>2</sub>) abilities during recovery following short all-out supramaximal exercise correlate with the muscle content of MCT1 and MCT4, the two isoforms of the monocarboxylate transporters family involved in lactate and H<sup>+</sup> co-transport in skeletal muscle. Eighteen lightweight rowers completed a 3-min all-out exercise on rowing ergometer. Blood lactate samples were collected during the subsequent passive recovery to assess an individual blood lactate curve (IBLC). IBLC were fitted to the bi-exponential time function: La(t) = [La](0) + A<sub>1</sub>(1 − <inline-formula><mml:math id="M1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mtext>e</mml:mtext><mml:mrow><mml:mo>-</mml:mo><mml:msubsup><mml:mrow><mml:mi>γ</mml:mi></mml:mrow><mml:mrow><mml:mn>1</mml:mn></mml:mrow><mml:mrow><mml:mtext>t</mml:mtext></mml:mrow></mml:msubsup></mml:mrow></mml:msup></mml:math></inline-formula>) + A<sub>2</sub>(1 − <inline-formula><mml:math id="M2" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mtext>e</mml:mtext><mml:mrow><mml:mo>-</mml:mo><mml:msubsup><mml:mrow><mml:mi>γ</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow><mml:mrow><mml:mtext>t</mml:mtext></mml:mrow></mml:msubsup></mml:mrow></mml:msup></mml:math></inline-formula>) where [La](0) is the blood lactate concentration at exercise completion and the velocity constants γ<sub>1</sub> and γ<sub>2</sub> denote the lactate exchange and removal abilities, respectively. An application of the bi-compartmental model of lactate distribution space allowed estimation of the lactate removal rate at exercise completion [LRR(0)]. Biopsy of the right <italic>vastus lateralis</italic> was taken at rest to measure muscle MCT1 and MCT4 content. Fiber type distribution, activity of key enzymes and capillary density (CD) were also assessed. γ<sub>1</sub> was correlated with [La](0) (<italic>r</italic> = −0.54, <italic>P</italic> &lt; 0.05) but not with MCT1, MCT4 or CD. γ<sub>2</sub> and LRR(0) were correlated with MCT4 (<italic>r</italic> = 0.63, <italic>P</italic> &lt; 0.01 and <italic>r</italic> = 0.73, <italic>P</italic> &lt; 0.001, respectively) but not with MCT1 or cytochrome c oxidase activity. These findings suggest that the lactate exchange ability is highly dependent on the milieu so that the importance of the muscle MCT1 and MCT4 content in γ<sub>1</sub> was hidden in the present study. Our results also suggest that during recovery following all-out supramaximal exercise in well-trained rowers, MCT4 might play a significant role in the distribution and delivery of lactate for its subsequent removal.</p>