Document Detail

Regulation of intracellular pH in the perfused heart by external HCO3- and Na(+)-H+ exchange.
MedLine Citation:
PMID:  8393626     Owner:  NLM     Status:  MEDLINE    
Both Na(+)-dependent HCO3- influx and the Na(+)-H+ antiport have been shown to contribute to recovery from intracellular acidosis in avian and mammalian cardiac tissue. We have investigated the participation of these mechanisms in the recovery of intracellular pH (pHi) after an acid load in the Langendorff-perfused ferret heart. pHi was measured from the phosphorus-31 nuclear magnetic resonance chemical shift of 2-deoxy-D-glucose 6-phosphate. Basal pHi was higher in HCO(3-)-buffered solution (7.05 +/- 0.01; n = 8) than in nominally HCO(3-)-free N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) solution (6.98 +/- 0.02; n = 9). Addition of 5-(N-ethyl-N-isopropyl)amiloride (EIPA) caused a significant fall in pHi in HEPES solution (6.91 +/- 0.02; n = 5) but not in HCO3- solution (7.02 +/- 0.02; n = 5). Intrinsic intracellular buffering capacity in 0 Na(+)-HEPES solution was 37 +/- 2 mmol/l (n = 4), and additional buffering due to HCO(3-)-CO2 was approximately 13 mmol/l in HCO3- solution. After an intracellular acidosis induced by an NH4Cl prepulse, the proton efflux rate (JH) at pHi 6.90 was 0.5 +/- 0.2 nmol.l-1.min-1 (n = 14) in HEPES solution and 1.2 +/- 0.4 mmol.l-1.min-1 (n = 13) in HCO3- solution. The addition of 1 microM EIPA effectively blocked proton efflux in HEPES solution (JH < 0.1 mmol.l-1.min-1; n = 8), whereas it slowed pHi recovery in HCO3- solution (JH = 0.6 +/- 0.2 mmol.l-1.min-1; n = 9). There was no recovery of pHi in Na(+)-free HCO3- solution (JH < 0.1 mmol.l-1.min-1; n = 3). The Na(+)-H+ antiport and a mechanism requiring both external Na+ and HCO3- each contribute approximately 50% to proton efflux at pHi 6.90 during the recovery from intracellular acidosis in the isolated perfused mammalian heart.
A A Grace; H L Kirschenlohr; J C Metcalfe; G A Smith; P L Weissberg; E J Cragoe; J I Vandenberg
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The American journal of physiology     Volume:  265     ISSN:  0002-9513     ISO Abbreviation:  Am. J. Physiol.     Publication Date:  1993 Jul 
Date Detail:
Created Date:  1993-08-27     Completed Date:  1993-08-27     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0370511     Medline TA:  Am J Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  H289-98     Citation Subset:  IM    
Department of Biochemistry, University of Cambridge, United Kingdom.
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MeSH Terms
Acids / pharmacology
Ammonium Chloride / pharmacology
Bicarbonates / pharmacology*
Carrier Proteins / physiology*
Glucose-6-Phosphate* / analogs & derivatives*
Glucosephosphates / pharmacology
Hydrogen-Ion Concentration
Intracellular Membranes / metabolism*
Myocardium / metabolism*
Sodium-Hydrogen Antiporter
Ventricular Function, Left
Reg. No./Substance:
0/Acids; 0/Bicarbonates; 0/Buffers; 0/Carrier Proteins; 0/Glucosephosphates; 0/Sodium-Hydrogen Antiporter; 12125-02-9/Ammonium Chloride; 3573-50-0/2-deoxyglucose-6-phosphate; 56-73-5/Glucose-6-Phosphate

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