Uptake of /sup 75/Se-selenite by brush border membrane vesicles from chick duodenum stimulated by vitamin D
Brush border membrane vesicles were isolated from mucosal homogenates of duodena from normal, rachitic and vitamin D-treated rachitic chicks using a discontinuous sucrose gradient, and further purified by glycerol gradient centrifugation. In vitro uptake of 75Se-selenite by purified brush border membrane vesicles was studied using a rapid filtration technique. The time course of 75Se uptake was non-linear; rapid initial binding was followed by a gradual decrease in the rate of uptake until an equilibrium value was reached at 60-120 min. The initial binding at 36 s was not affected by selenite concentration in the incubation buffer, while the fractional rate of uptake between the 36 s and 2 min time periods was clearly lower with 1 mM Se than with 4-100 microM Se. 75Se uptake did not show any dependency on the external Na-gradient, nor could it be inhibited by other anions (arsenate, phosphate). Treatment of rachitic chicks either with cholecalciferol (500 Iu, 72 h) or with 1,25(OH)2-cholecalciferol (0.5 microgram given 16 h prior to isolation of the vesicles) significantly enhanced 75Se uptake. A threefold excess of mannitol in the outside buffer reduced 75Se uptake by vesicles from vitamin D-deficient and D-treated chicks 60% and 35% respectively, but had no effect on vesicles from vitamin D-treated chicks preloaded with 75Se. Neither saponin treatment nor excess cold selenite could release the label from the vesicles preloaded with 75Se. These data are compatible with the hypothesis that selenite easily crosses the brush border membrane into the intravesicular space and, once inside, is tightly bound by the membrane.
- Research Organization:
- Cornell Univ., Ithaca (USA)
- OSTI ID:
- 6071798
- Journal Information:
- J. Nutr.; (United States), Vol. 119:2
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
SELENIUM
INTESTINAL ABSORPTION
VITAMIN D
BIOLOGICAL EFFECTS
ARSENATES
CELL MEMBRANES
CHICKENS
IN VITRO
METABOLISM
PHOSPHATES
RESPONSE MODIFYING FACTORS
SAPONINS
SELENIUM 75
SMALL INTESTINE
SODIUM
TRACER TECHNIQUES
ULTRACENTRIFUGATION
ABSORPTION
ALKALI METALS
ANIMALS
ARSENIC COMPOUNDS
BETA DECAY RADIOISOTOPES
BIRDS
BODY
CARBOHYDRATES
CELL CONSTITUENTS
CENTRIFUGATION
DAYS LIVING RADIOISOTOPES
DIGESTIVE SYSTEM
ELECTRON CAPTURE RADIOISOTOPES
ELEMENTS
EVEN-ODD NUCLEI
FOWL
GASTROINTESTINAL TRACT
GLYCOSIDES
INTERMEDIATE MASS NUCLEI
INTESTINES
ISOTOPE APPLICATIONS
ISOTOPES
MEMBRANES
METALS
NUCLEI
ORGANIC COMPOUNDS
ORGANS
OXYGEN COMPOUNDS
PHOSPHORUS COMPOUNDS
RADIOISOTOPES
SELENIUM ISOTOPES
SEMIMETALS
SEPARATION PROCESSES
UPTAKE
VERTEBRATES
VITAMINS
560300* - Chemicals Metabolism & Toxicology
550501 - Metabolism- Tracer Techniques