title: Exhausting exercise and tissue-specific expression of monocarboxylate transporters in rainbow trout.
abstract: Transmembrane lactate movements are mediated by monocarboxylate transporters (MCTs), but these proteins have never been characterized in rainbow trout. Our goals were to clone potential trout MCTs, determine tissue distribution, and quantify the effects of exhausting exercise on MCT expression. Such information could prove important to understand the mechanisms underlying the classic "lactate retention" seen in trout white muscle after intense exercise. Four isoforms were identified and partially characterized in rainbow trout: MCT1a, MCT1b, MCT2, and MCT4. MCT1b was the most abundant in heart and red muscle but poorly expressed in the gill and brain where MCT1a and MCT2 were prevalent. MCT expression was strongly stimulated by exhausting exercise in brain (MCT2: +260%) and heart (MCT1a: +90% and MCT1b: +50%), possibly to increase capacity for lactate uptake in these highly oxidative tissues. By contrast, the MCTs of gill, liver, and muscle remained unaffected by exercise. This study provides a possible functional explanation for postexercise "lactate retention" in trout white muscle. Rainbow trout may be unable to release large lactate loads rapidly during recovery because: 1) they only poorly express MCT4, the main lactate exporter found in mammalian glycolytic muscles; 2) the combined expression of all trout MCTs is much lower in white muscle than in any other tissue; and 3) exhausting exercise fails to upregulate white muscle MCT expression. In this tissue, carbohydrates act as an "energy spring" that alternates between explosive power release during intense swimming (glycogen to lactate) and recoil during protracted recovery (slow glycogen resynthesis from local lactate).
authors.affiliation: Biology Department and Center for Advanced Research in Environmental Genomics (CAREG), University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Teye
authors.initials: T
authors.lastname: Omlin
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Weber
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001923:Brain Chemistry / Q000502:physiology; D003001:Cloning, Molecular; D017931:DNA Primers; D005260:Female; D005880:Gills / Q000378:metabolism; D007536:Isomerism; D007700:Kinetics; D019344:Lactic Acid / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D027501:Monocarboxylic Acid Transporters / Q000235:genetics / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D017686:Oncorhynchus mykiss / Q000378:metabolism / Q000502:physiology*; D010802:Phylogeny; D005082:Physical Exertion / Q000502:physiology*; D060888:Real-Time Polymerase Chain Reaction; D013550:Swimming / Q000502:physiology
chemical_list: D017931:DNA Primers; D027501:Monocarboxylic Acid Transporters; D019344:Lactic Acid
keywords: MCT gene expression; Oncorhynchus mykiss; anaerobic metabolism; fish white muscle; intense swimming; lactate retention; transmembrane lactate transport
references.citation: Annu Rev Physiol. 1996;58:565-81
references.pmid: 8815809
references.citation: J Exp Biol. 1978 Dec;77:141-55
references.pmid: 752060
references.citation: Med Sci Sports Exerc. 1991 Aug;23(8):895-906
references.pmid: 1956262
references.citation: Bioinformatics. 2001 Aug;17(8):754-5
references.pmid: 11524383
references.citation: Biochem Soc Trans. 2002 Apr;30(2):258-64
references.pmid: 12023861
references.citation: PLoS One. 2012;7(4):e34579
references.pmid: 22496829
references.citation: J Exp Biol. 2010 Nov 15;213(Pt 22):3802-9
references.pmid: 21037059
references.citation: Biotechnol Lett. 2004 Mar;26(6):509-15
references.pmid: 15127793
references.citation: Bioinformatics. 2003 Aug 12;19(12):1572-4
references.pmid: 12912839
references.citation: Am J Physiol. 1992 Feb;262(2 Pt 2):R245-54
references.pmid: 1539733
references.citation: Am J Physiol Endocrinol Metab. 2000 Nov;279(5):E1131-8
references.pmid: 11052969
references.citation: J Exp Biol. 1999;202(Pt 16):2167-2175
references.pmid: 10409488
references.citation: Appl Physiol Nutr Metab. 2006 Feb;31(1):31-9
references.pmid: 16604139
references.citation: Am J Physiol Regul Integr Comp Physiol. 2012 Jan 1;302(1):R1-14
references.pmid: 22012699
references.citation: J Neurosci. 1997 Dec 15;17(24):9448-57
references.pmid: 9391000
references.citation: J Neurochem. 1997 Jul;69(1):423-6
references.pmid: 9202338
references.citation: J Exp Biol. 2000 Mar;203(Pt 5):921-6
references.pmid: 10667975
references.citation: Comp Biochem Physiol B Biochem Mol Biol. 2009 Dec;154(4):396-405
references.pmid: 19709642
references.citation: J Exp Biol. 1991 Jul;158:463-76
references.pmid: 1919415
references.citation: J Physiol. 2004 Nov 15;561(Pt 1):253-61
references.pmid: 15388779
references.citation: Pflugers Arch. 2004 Feb;447(5):619-28
references.pmid: 12739169
references.citation: Am J Physiol Regul Integr Comp Physiol. 2010 Aug;299(2):R579-89
references.pmid: 20519364
references.citation: Am J Physiol. 1997 May;272(5 Pt 2):R1577-87
references.pmid: 9176350
references.citation: J Cereb Blood Flow Metab. 2003 Jun;23(6):658-64
references.pmid: 12796713
references.citation: J Mol Evol. 2010 May;70(5):492-505
references.pmid: 20443112
references.citation: Acta Physiol (Oxf). 2010 Aug;199(4):499-508
references.pmid: 20345411
references.citation: Biochim Biophys Acta. 1988 Oct 6;944(2):213-22
references.pmid: 2846055
references.citation: Nucleic Acids Res. 2001 May 1;29(9):e45
references.pmid: 11328886
references.citation: Science. 1988 Jun 3;240(4857):1326-8
references.pmid: 3375817
references.citation: J Exp Biol. 2003 Feb;206(Pt 3):543-9
references.pmid: 12502775
references.citation: Comp Biochem Physiol B Biochem Mol Biol. 1998 May;120(1):89-107
references.pmid: 9787780
references.citation: Neurosci Res. 1996 Dec;26(4):369-76
references.pmid: 9004275
references.citation: Xenobiotica. 2008 Jul;38(7-8):1072-106
references.pmid: 18668440
references.citation: Biochem J. 1999 Oct 15;343 Pt 2:281-99
references.pmid: 10510291
references.citation: IUBMB Life. 2012 Feb;64(2):109-19
references.pmid: 22162139
references.citation: J Neurochem. 1995 Apr;64(4):1734-41
references.pmid: 7891102
references.citation: J Physiol. 2004 Jul 1;558(Pt 1):5-30
references.pmid: 15131240
references.citation: Eur J Appl Physiol. 2006 Apr;96(6):636-43
references.pmid: 16408234
references.citation: Can J Zool. 1980 Sep;58(9):1708-11
references.pmid: 7459747
references.citation: J Exp Biol. 1996;199(Pt 5):1157-62
references.pmid: 9318994