An electrogenic sodium-bicarbonate cotransport in the regulation of myocardial intracellular pH

M. C. Camilion de Hurtado, N. G. Perez, H. E. Cingolani

Research output: Contribution to journalArticle

Abstract

Experiments were performed in cat papillary muscles in order to explore the possible existence of an electrogenic Na+/HCO3- cotransport. Developed tension (DT), intracellular pH (pH(i)) with the pH-sensitive dye 2'-7'-bis(2-carboxyethyl)-5,6-carboxyfluorescein (BCECF) and resting membrane potential (V(m)) with 3M KCl filled glass microelectrodes were measured. A change from HEPES to HCO3--buffered superfusate induced an immediate decrease in pH(i) and DT followed by a recovery in which pH(i) and DT stabilized at values slightly higher than in HEPES buffer. Introduction of HCO3- hyperpolarized V(m) by 8 ± 2.3 mV (P < 0.05). SITS (0.1mM) completely abolished the hyperpolarization and attenuated the recovery of both pH(i) and DT. Under steady-state conditions in HCO3- buffered media, SITS induced a depolarization compatible with the suppression of the entry of negative charges. Depolarization by high K(o)+ (45 mM) elicited a rise in pH(i) of 0.07 ± 0.02 (P < 0.05), that was reversed by returning K(o)+ to normal. The depolarization-induced rise in pH(i) proved to be Na+-dependent, SITS sensitive and still occurred after EIPA (μM) blockade. All the evidence strongly supports the existence of an electrogenic Na+/HCO3- cotransport mechanism that participates in the regulation of myocardial pH(i). At pH(i) of 6.94 this mechanism seems to contribute almost equally to the Na+/H+ exchanger to pH(i) regulation. However, acid equivalent extrusion is potentiated when both the Na+/H+ exchanger and the HCO3--dependent mechanism are simultaneously regulating pH(i).

Original languageEnglish (US)
Pages (from-to)231-242
Number of pages12
JournalJournal of Molecular and Cellular Cardiology
Volume27
Issue number1
StatePublished - Jan 1 1995

Keywords

  • BCECF
  • EIPA
  • Intracellular pH
  • Myocardium
  • Na/HCO(*)-cotransport
  • Resting membrane potential
  • SITS
  • pH(i) recovery

ASJC Scopus subject areas

  • Molecular Biology
  • Cardiology and Cardiovascular Medicine

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