Potassium depletion increases luminal Na+/H+ exchange and basolateral Na+:CO3=:HCO3- cotransport in rat renal cortex

Journal Article · Mon Oct 01 00:00:00 EDT 1990 · Journal of Clinical Investigation; (USA)

DOI:https://doi.org/10.1172/JCI114810· OSTI ID:6217635

Soleimani, M; Bergman, J A; Hosford, M A; McKinney, T D ^[1]

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1. Indiana Univ. Medical Center, Indianapolis (USA)

Most HCO3- reabsorption in proximal tubules occurs via electroneutral Na+/H+ exchange in brush border membranes (BBMS) and electrogenic Na+:CO3=:HCO3- cotransport in basolateral membranes (BLMS). Since potassium depletion (KD) increases HCO3- reabsorption in proximal tubules, we evaluated these transport systems using BBM and BLM vesicles, respectively, from control (C) and KD rats. Feeding rats a potassium deficient diet for 3-4 wk resulted in lower plasma (K+) (2.94 mEq/liter, KD vs. 4.47 C), and higher arterial pH (7.51 KD vs. 7.39 C). KD rats gained less weight than C but had higher renal cortical weight. Influx of 1 mM 22Na+ at 5 s (pHo 7.5, pHi 6.0, 10% CO2, 90% N2) into BLM vesicles was 44% higher in the KD group compared to C with no difference in equilibrium uptake. The increment in Na+ influx in the KD group was DIDS sensitive, suggesting that Na+:CO3=:HCO3- cotransport accounted for the observed differences. Kinetic analysis of Na+ influx showed a Km of 8.2 mM in KD vs. 7.6 mM in C and Vmax of 278 nmol/min/mg protein in KD vs. 177 nmol/min/mg protein in C. Influx of 1 mM 22Na+ at 5 s (pHo 7.5, pHi 6.0) into BBM vesicles was 34% higher in the KD group compared to C with no difference in equilibrium uptake. The increment in Na+ influx in the KD group was amiloride sensitive, suggesting that Na+/H+ exchange was responsible for the observed differences. Kinetic analysis of Na+ influx showed a Km of 6.2 mM in KD vs. 7.1 mM in C and Vmax of 209 nmol/min/mg protein in KD vs. 144 nmol/min/mg protein in C. Uptakes of Na(+)-dependent (3H)glucose into BBM and (14C)succinate into BLM vesicles were not different in KD and C groups, suggesting that the Na+/H+ exchanger and Na+:CO3=:HCO3- cotransporter activities were specifically altered in KD.

• OSTI ID: 6217635
• Journal Information: Journal of Clinical Investigation; (USA), Vol. 86:4; ISSN 0021-9738
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
ACID CARBONATES
MEMBRANE TRANSPORT
POTASSIUM
BIOCHEMICAL REACTION KINETICS
SODIUM COMPOUNDS
CARBON 14 COMPOUNDS
CELL MEMBRANES
ION EXCHANGE
PROTONS
RATS
SODIUM 22
TRACER TECHNIQUES
TUBULES
ALKALI METAL COMPOUNDS
ALKALI METAL ISOTOPES
ALKALI METALS
ANIMALS
BARYONS
BETA DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
BODY
CELL CONSTITUENTS
ELEMENTARY PARTICLES
ELEMENTS
FERMIONS
HADRONS
ISOMERIC TRANSITION ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KIDNEYS
KINETICS
LABELLED COMPOUNDS
LIGHT NUCLEI
MAMMALS
MEMBRANES
METALS
NUCLEI
NUCLEONS
ODD-ODD NUCLEI
ORGANS
RADIOISOTOPES
REACTION KINETICS
RODENTS
SODIUM ISOTOPES
VERTEBRATES
YEARS LIVING RADIOISOTOPES
550201* - Biochemistry- Tracer Techniques