title: Functional interaction between bicarbonate transporters and carbonic anhydrase modulates lactate uptake into mouse cardiomyocytes.
abstract: Blood-derived lactate is a precious energy substrate for the heart muscle. Lactate is transported into cardiomyocytes via monocarboxylate transporters (MCTs) together with H(+), which couples lactate uptake to cellular pH regulation. In this study, we have investigated how the interplay between different acid/base transporters and carbonic anhydrases (CA), which catalyze the reversible hydration of CO2, modulates the uptake of lactate into isolated mouse cardiomyocytes. Lactate transport was estimated both as lactate-induced acidification and as changes in intracellular lactate levels measured with a newly developed Förster resonance energy transfer (FRET) nanosensor. Recordings of intracellular pH showed an increase in the rate of lactate-induced acidification when CA was inhibited by 6-ethoxy-2-benzothiazolesulfonamide (EZA), while direct measurements of lactate flux demonstrated a decrease in MCT transport activity, when CA was inhibited. The data indicate that catalytic activity of extracellular CA increases lactate uptake and counteracts intracellular lactate-induced acidification. We propose a hypothetical model, in which HCO3 (-), formed from cell-derived CO2 at the outer surface of the cardiomyocyte plasma membrane by membrane-anchored, extracellular CA, is transported into the cell via Na(+)/HCO3 (-) cotransport to counteract intracellular acidification, while the remaining H(+) stabilizes extracellular pH at the surface of the plasma membrane during MCT activity to enhance lactate influx into cardiomyocytes.
authors.affiliation: Division of Zoology/Membrane Transport, FB Biologie, TU Kaiserslautern, P.O. Box 3049, 67653, Kaiserslautern, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Peetz
authors.affiliation: Centro de Estudios Científicos (CECs), Valdivia, Chile.
authors.forename: L Felipe
authors.initials: LF
authors.lastname: Barros
authors.affiliation: Centro de Estudios Científicos (CECs), Valdivia, Chile.
authors.forename: Alejandro
authors.initials: A
authors.lastname: San Martín
authors.affiliation: Division of Zoology/Membrane Transport, FB Biologie, TU Kaiserslautern, P.O. Box 3049, 67653, Kaiserslautern, Germany. h.becker@biologie.uni-kl.de.
authors.forename: Holger M
authors.initials: HM
authors.lastname: Becker
mesh_terms: D000818:Animals; D052160:Benzothiazoles / Q000494:pharmacology; D001639:Bicarbonates / Q000378:metabolism; D015374:Biosensing Techniques; D002257:Carbonic Anhydrase Inhibitors / Q000494:pharmacology; D002256:Carbonic Anhydrases / Q000378:metabolism*; D002478:Cells, Cultured; D031541:Fluorescence Resonance Energy Transfer; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D027501:Monocarboxylic Acid Transporters / Q000037:antagonists & inhibitors / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism*; D027982:Sodium-Bicarbonate Symporters / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013449:Sulfonamides / Q000494:pharmacology; D027981:Symporters / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000099233:Monocarboxylate Transport Protein 1
chemical_list: D052160:Benzothiazoles; D001639:Bicarbonates; D002257:Carbonic Anhydrase Inhibitors; D002256:Carbonic Anhydrases; D019344:Lactic Acid; D027501:Monocarboxylic Acid Transporters; D027982:Sodium-Bicarbonate Symporters; D013449:Sulfonamides; D027981:Symporters; D000099233:Monocarboxylate Transport Protein 1; C523270:6-ethoxybenzothiazole-2-sulfonamide