Na sup + uptake into colonic enterocyte membrane vesicles

Journal Article · Fri Apr 01 04:00:00 EST 1988 · American Journal of Physiology; (USA)

OSTI ID:6749541

Bridges, R J; Garty, H; Benos, D J; Rummel, W ^[1]

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1. Univ. of Saarland, Hamburg (West Germany) Weizmann Institute of Science, Rehovot (Israel) Univ. of Alabama, Birmingham (USA)

Na{sup +} uptake was studied in colonic enterocyte membrane vesicles prepared from normal and dexamethasone-treated rats. Vesicles from rats treated with dexamethasone demonstrated a fivefold greater {sup 22}Na{sup +} uptake compared with vesicles from normal rats. Most of the tracer uptake in membranes derived from treated rats occurred through a conductive, amiloride-blockable pathway located in vesicles with low native K{sup +} permeability and high Cl{sup {minus}} permeability. Kinetic analysis of the amiloride inhibition curve revealed the presence of two amiloride-blockable pathways, one with a high affinity accounting for 85% of the uptake, and one with a low affinity accounting for only 12% of the uptake. Only the low-affinity pathway was detected with vesicles from normal rats. The high sensitivity to amiloride, the dependence on dexamethasone pretreatment, and the relative permeabilities to K{sup +} and Cl{sup {minus}} indicate that most of the {sup 22}Na{sup +} uptake in membranes derived from treated rats is through a Na{sup +}-specific channel located in apical membrane vesicles. Preincubation of the isolated cells from dexamethasone-treated rats at 37{degree}C in Ca{sup 2+}-free solutions before homogenization and membrane vesicle purification caused a 5- to 10-fold increase in amiloride-blockable {sup 22}Na{sup +} uptake compared with vesicles derived from cells maintained at 0{degree}C. The addition of Ca{sup 2+}, but not of Mg{sup 2+}, to the incubation solution markedly reduced this temperature-dependent enhancement in {sup 22}Na{sup +} uptake. These results suggest that Na{sup +} transport in colonic enterocytes from dexamethasone-treated rats is regulated by a Ca{sup 2+}-dependent, temperature-sensitive process which causes a sustained change in the apical membrane.

• OSTI ID: 6749541
• Journal Information: American Journal of Physiology; (USA), Journal Name: American Journal of Physiology; (USA) Vol. 254:4; ISSN 0002-9513; ISSN AJPHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ADRENAL HORMONES
ALKALI METAL ISOTOPES
ALKALINE EARTH METAL COMPOUNDS
ANIMAL CELLS
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BODY
CALCIUM COMPOUNDS
CELL CONSTITUENTS
CELL MEMBRANES
CORTICOSTEROIDS
DEXAMETHASONE
DIGESTIVE SYSTEM
DIURETICS
DRUGS
GASTROINTESTINAL TRACT
GLUCOCORTICOIDS
HYDROXY COMPOUNDS
INTESTINES
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
KETONES
KINETICS
LIGHT NUCLEI
MAGNESIUM COMPOUNDS
MAMMALS
MEMBRANE TRANSPORT
MEMBRANES
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANS
PERMEABILITY
PREGNANES
RADIOISOTOPES
RATS
REACTION KINETICS
RODENTS
SODIUM 22
SODIUM ISOTOPES
STEROIDS
UPTAKE
VERTEBRATES
YEARS LIVING RADIOISOTOPES