Na+ electrochemical gradient and Na+-Ca2+ exchange in rat proximal tubule

Journal Article · Sun Oct 01 00:00:00 EDT 1989 · American Journal of Physiology; (USA)

OSTI ID:5161459

Dominguez, J H; Rothrock, J K; Macias, W L; Price, J ^[1]

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1. Veterans Administration Medical Center, Indianapolis, IN (USA)

The basolateral cell membrane of the rat proximal tubule contains a Na+-Ca2+ exchanger that may participate in the regulation of cytosolic calcium (Cai) and Ca2+ transport. In this work, the activity and orientation of the Na+-Ca2+ exchanger was studied in rat proximal tubules. The experiments were based on the thermodynamic notion that the exchanger is driven by the prevalence of either of two electrochemical gradients, that for Na+ (delta mu Na+) or for Ca2+ (delta mu Ca2+). Reductions in delta mu Na+, achieved by lowering extracellular Na+ (Nao) from 150 to 15 mM, increased Cai, decreased 45Ca efflux, and increased 45Ca influx. These changes occurred concurrently. When delta mu Na+ was reduced by increasing intracellular Na+ (Nai) with 10(-3) M oubain, Cai also increased. The effect of ouabain was probably dependent on Nai accumulation because the surge in Cai was prevented by exposure of the tubules to 5 mM Nao before ouabain exposure. On the other hand, when delta mu Na+ was lowered mM Nao and then by reducing Nao to 15 mM, Cai rose in two additive stages. We conclude from these data that in the rat proximal tubule the basal state of the Na+-Ca2+ exchanger is in forward mode, Nao-Cai. Moreover, the function of the Na+-Ca2+ exchanger is in accord with predictions derived from a thermodynamic analysis of its function.

• OSTI ID: 5161459
• Journal Information: American Journal of Physiology; (USA), Vol. 257; ISSN 0002-9513
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
CALCIUM
MEMBRANE TRANSPORT
SODIUM COMPOUNDS
BIOCHEMICAL REACTION KINETICS
CALCIUM 45
IN VITRO
ISOTOPE DILUTION
OUABAIN
RATS
TUBULES
ALKALI METAL COMPOUNDS
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METALS
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BODY
CALCIUM ISOTOPES
CARBOHYDRATES
CARDIAC GLYCOSIDES
CARDIOTONICS
CARDIOVASCULAR AGENTS
DAYS LIVING RADIOISOTOPES
DRUGS
ELEMENTS
EVEN-ODD NUCLEI
GLYCOSIDES
INTERMEDIATE MASS NUCLEI
ISOTOPE APPLICATIONS
ISOTOPES
KIDNEYS
KINETICS
MAMMALS
METALS
NUCLEI
ORGANIC COMPOUNDS
ORGANS
RADIOISOTOPES
REACTION KINETICS
RODENTS
STROPHANTHINS
TRACER TECHNIQUES
VERTEBRATES
550201* - Biochemistry- Tracer Techniques