Ammonium ion substitutes for K/sup +/ in ATP-dependent Na/sup +/ transport by basolateral membrane vesicles

Journal Article · Sat Feb 28 23:00:00 EST 1987 · Am. J. Physiol.; (United States)

OSTI ID:5964452

Towle, D W; Hoelleland, T

Ion-transporting cells from posterior gills of blue crabs (Callinectes sapidus) acclimated to low salinity were used as starting material for the preparation of microsomal membrane vesicles by density gradient centrifugation. The Na/sup +/-K/sup +/-adenosinetriphosphatase (ATPase)-enriched basolateral vesicles were loaded with KCl- or NH/sub 4//sup +/-containing medium by dilution and centrifugation, and initial rates of /sup 22/Na/sup +/ uptake into the vesicles were measured by a rapid filtration procedure. Varying the extravesicular sucrose concentration altered equilibrium uptake of /sup 22/Na/sup +/, indicating the existence of osmotically sensitive vesicles. Monensin, a sodium-specific ionophore, enhanced passive uptake of /sup 22/Na/sup +/ across the vesicle membrane in the absence of ATP. With 100 mM KCl in the intravesicular medium, addition of ATP to the extravesicular medium increased initial rates of /sup 22/Na/sup +/ uptake 10- to 20-fold over levels measured without ATP. A nonhydrolyzable ATP analog failed to stimulate /sup 22/Na/sup +/ uptake. Intravesicular K/sup +/ could be replaced by NH/sub 4//sup +/ but not by choline. With NH/sub 4//sup +/ as counterion, Na/sup +/ transport was inhibited by digitoxin, but valinomycin had no effect. A study of the kinetic effects of intravesicular K/sup +/ and NH/sub 4//sup +/ on initial rates of /sup 22/Na/sup +/ uptake indicated the existence of two classes of binding sites, one responding to counterion concentrations in the millimolar range and a second class responding to counterion concentrations over 50 mM. The results indicate that ATP-dependent /sup 22/Na/sup +/ uptake by membrane vesicles from Callinectes sapidus gill, mediated by Na/sup +/-K/sup +/-ATPase, can utilize either K/sup +/ or NH/sub 4//sup +/ as counterion.

• Research Organization: Univ. of Richmond, VA
• OSTI ID: 5964452
• Journal Information: Am. J. Physiol.; (United States), Journal Name: Am. J. Physiol.; (United States) Vol. 252:3; ISSN AJPHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ACID ANHYDRASES
ALKALI METAL COMPOUNDS
ALKALI METAL ISOTOPES
AMMONIUM COMPOUNDS
ANIMALS
AQUATIC ORGANISMS
ARTHROPODS
ATP-ASE
BETA DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
CATIONS
CELL CONSTITUENTS
CELL MEMBRANES
CHARGED PARTICLES
CHLORIDES
CHLORINE COMPOUNDS
CRABS
CRUSTACEANS
DECAPODS
DOSE-RESPONSE RELATIONSHIPS
ELECTRON MICROSCOPY
ENZYMES
HALIDES
HALOGEN COMPOUNDS
HYDROLASES
INVERTEBRATES
IONS
ISOTOPES
KINETICS
LIGHT NUCLEI
MEMBRANE TRANSPORT
MEMBRANES
MICROSCOPY
NUCLEI
ODD-ODD NUCLEI
PHOSPHOHYDROLASES
POTASSIUM CHLORIDES
POTASSIUM COMPOUNDS
RADIOISOTOPES
REACTION KINETICS
SODIUM 22
SODIUM COMPOUNDS
SODIUM ISOTOPES
TEMPERATURE DEPENDENCE
TRANSMISSION ELECTRON MICROSCOPY
UPTAKE
YEARS LIVING RADIOISOTOPES