HCO3(-)-coupled Na+ influx is a major determinant of Na+ turnover and Na+/K+ pump activity in rat hepatocytes

Journal Article · Wed May 01 04:00:00 EDT 1991 · Journal of Membrane Biology; (United States)

DOI:https://doi.org/10.1007/BF01872734· OSTI ID:5266342

Fitz, J G; Lidofsky, S D; Weisiger, R A; Xie, M H; Cochran, M; Grotmol, T; Scharschmidt, B F ^[1]

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1. University of California, San Francisco (USA)

Recent studies in hepatocytes indicate that Na(+)-coupled HCO3- transport contributes importantly to regulation of intracellular pH and membrane HCO3- transport. However, the direction of net coupled Na+ and HCO3- movement and the effect of HCO3- on Na+ turnover and Na+/K+ pump activity are not known. In these studies, the effect of HCO3- on Na+ influx and turnover were measured in primary rat hepatocyte cultures with 22Na+, and (Na+)i was measured in single hepatocytes using the Na(+)-sensitive fluorochrome SBFI. Na+/K+ pump activity was measured in intact perfused rat liver and hepatocyte monolayers as Na(+)-dependent or ouabain-suppressible 86Rb uptake, and was measured in single hepatocytes as the effect of transient pump inhibition by removal of extracellular K+ on membrane potential difference (PD) and (Na+)i. In hepatocyte monolayers, HCO3- increased 22Na+ entry and turnover rates by 50-65%, without measurably altering 22Na+ pool size or cell volume, and HCO3- also increased Na+/K+ pump activity by 70%. In single cells, exposure to HCO3- produced an abrupt and sustained rise in (Na+)i from approximately 8 to 12 mM. Na+/K+ pump activity assessed in single cells by PD excursions during transient K+ removal increased congruent to 2.5-fold in the presence of HCO3-, and the rise in (Na+)i produced by inhibition of the Na+/K+ pump was similarly increased congruent to 2.5-fold in the presence of HCO3-. In intact perfused rat liver, HCO3- increased both Na+/K+ pump activity and O2 consumption. These findings indicate that, in hepatocytes, net coupled Na+ and HCO3- movement is inward and represents a major determinant of Na+ influx and Na+/K+ pump activity. About half of hepatic Na+/K+ pump activity appears dedicated to recycling Na+ entering in conjunction with HCO3- to maintain (Na+)i within the physiologic range.

• OSTI ID: 5266342
• Journal Information: Journal of Membrane Biology; (United States), Journal Name: Journal of Membrane Biology; (United States) Vol. 122:1; ISSN JMBBB; ISSN 0022-2631
• Country of Publication: United States
• Language: English

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59 BASIC BIOLOGICAL SCIENCES
ACID CARBONATES
ALKALI METAL COMPOUNDS
ALKALI METAL ISOTOPES
ANIMAL CELLS
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
BODY
CARBOHYDRATES
CARDIAC GLYCOSIDES
CARDIOTONICS
CARDIOVASCULAR AGENTS
DAYS LIVING RADIOISOTOPES
DIGESTIVE SYSTEM
DRUGS
ELECTRON CAPTURE RADIOISOTOPES
ELEMENTS
GLANDS
GLYCOSIDES
INTERMEDIATE MASS NUCLEI
ISOMERIC TRANSITION ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
LIVER
LIVER CELLS
MAMMALS
MEMBRANE TRANSPORT
METABOLISM
MINUTES LIVING RADIOISOTOPES
NANOSEC LIVING RADIOISOTOPES
NONMETALS
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANS
OUABAIN
OXYGEN
PERFUSED ORGANS
POTASSIUM COMPOUNDS
RADIOISOTOPES
RATS
RODENTS
RUBIDIUM 86
RUBIDIUM ISOTOP
SODIUM 22
SODIUM COMPOUNDS
SODIUM ISOTOPES
SOMATIC CELLS
STROPHANTHINS
TRACER TECHNIQUES
VERTEBRATES
YEARS LIVING RADIOISOTOPES