Lactate and metabolic H+ transport and distribution after exercise in rainbow trout white muscle

Yuxiang Wang, George J.F. Heigenhauser, Chris M. Wood

Research output: Contribution to journalArticle

6 Scopus citations

Abstract

An isolated-perfused tail-trunk preparation was employed to study the influence of transmembrane pH gradient and membrane potential on the transport and distribution of L(+)-lactate (Lac), metabolic H+ (ΔH(m)/+), and related parameters in rainbow trout white muscle after exhaustive exercise. One resting [arterial pH (pH(a)) ≃ 7.9] and four postexercise treatments (pH(a) ≃ 7.4, 7.9, 8.4, and, high K+, pH(a) ≃ 7.9, partially depolarized by 15 mM K+) were examined. Variations in HCO3/- concentration (2-18mM) at a constant PCO2 ≃2 Torr were used to alter pH(a). The elevated intracellular Lac (≃50 mM) remained unchanged after 60 min of perfusion because of very low rates of lactate efflux and oxidation. H+, HCO3/- and Lac distributions were all well out of electrochemical equilibrium. Total CO2 efflux was reduced at high extracellular pH (pH(e)); alterations in the net driving force on HCO3/- may have overshadowed the influence of PCO2 gradients in driving total CO2 efflux. Lac efflux and ΔH(m)/+ flux were completely uncoupled. ΔH(m)/+ flux reacted to both acid-base and electrochemical gradients as ΔH(m)/+ efflux dropped and even reversed when pH(e) decreased, whereas partial depolarization in conjunction with depressed intracellular pH resulted in elevated ΔH(m)/+ efflux. Lac efflux did not respond to changes in pH(e). Changes in Lac efflux corresponded more closely to changes in the Lac concentration gradient than in the lactic acid gradient. This study provides circumstantial evidence for the involvement of electroneutral mechanisms (i.e., Lac -H+ cotransport and/or Lac/anion exchange) in lactate efflux, but does not eliminate the possibility of an active transport mechanism contributing to the retention of Lac.

Original languageEnglish (US)
Pages (from-to)R1239-R1250
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume271
Issue number5 40-5
DOIs
StatePublished - Nov 1996

Keywords

  • bicarbonate
  • carbon dioxide
  • exercise
  • extracellular pH
  • intracellular pH
  • metabolic acid
  • Nernst potential
  • oxygen
  • perfusion

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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