Characterization of calcium transport by basolateral membrane vesicles of human small intestine

Journal Article · Sat Oct 01 00:00:00 EDT 1988 · American Journal of Physiology; (USA)

OSTI ID:6037168

Kikuchi, Kazuhiro; Kikuchi, Toshiko; Ghishan, F K ^[1]

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1. Vanderbilt Univ. School of Medicine, Nashville, TN (USA)

The present studies investigated the mechanism of Ca{sup 2+} transport across basolateral membrane vesicles (BLMVs) prepared from human small intestine. Ca{sup 2+} uptake represented transport into the intravesicular space as evident by osmolality study and by the demonstration of Ca{sup 2+} efflux from the intravesicular space by Ca{sup 2+} ionophore A23187. Ca{sup 2+} uptake was stimulated by Mg{sup 2+}-ATP. Kinetic parameters for ATP-dependent Ca{sup 2+} uptake revealed a Michaelis constant (K{sub m}) of 0.02{plus minus}0.01 {mu}M and a maximum rate of uptake (V{sub max}) of 1.00{plus minus}0.03 nmol{center dot}mg protein{sup {minus}1}{center dot}min{sup {minus}1}. Ca{sup 2+} uptake in the presence of Mg{sup 2+} was inhibited by 75%. The K{sub m} of ATP concentration required for half-maximal Ca{sup 2+} uptake was 0.50{plus minus}0.1 mM. Basolateral membranes depleted of calmodulin by EDTA osmotic shock decreased ATP-dependent Ca{sup 2+} uptake by 65%. Trifluoperazine, an anticalmodulin drug, inhibited ATP-dependent Ca{sup 2+} uptake by 50%, while no inhibition was noted in calmodulin-depleted membranes. Efflux of Ca{sup 2+} in the BLMVs was stimulated by trans-Na{sup +}. Na{sup +}-dependent Ca{sup 2+} uptake was saturable with respect to Ca{sup 2+} concentration and exhibited a K{sub m} of 0.09{plus minus}0.03 {mu}M and a V{sub max} of 1.08{plus minus}0.01 nmol{center dot}mg protein{sup {minus}1}{center dot}min{sup {minus}1}. These results are consistent with the existence of a Na{sup +}-Ca{sup 2+} exchange system and ATP and Mg{sup 2+}-dependent, calmodulin-regulated Ca{sup 2+}, transport mechanism in BLMVs of human enterocytes.

• OSTI ID: 6037168
• Journal Information: American Journal of Physiology; (USA), Vol. 255:4; ISSN 0002-9513
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
CALCIUM 45
UPTAKE
MEMBRANE TRANSPORT
BIOCHEMICAL REACTION KINETICS
SMALL INTESTINE
PHYSIOLOGY
ATP
EDTA
GLUCOSE
MAN
MEMBRANES
TRITIUM COMPOUNDS
ALDEHYDES
ALKALINE EARTH ISOTOPES
AMINO ACIDS
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BODY
CALCIUM ISOTOPES
CARBOHYDRATES
CARBOXYLIC ACIDS
CHELATING AGENTS
DAYS LIVING RADIOISOTOPES
DIGESTIVE SYSTEM
EVEN-ODD NUCLEI
GASTROINTESTINAL TRACT
HEXOSES
HYDROGEN COMPOUNDS
INTERMEDIATE MASS NUCLEI
INTESTINES
ISOTOPES
KINETICS
MAMMALS
MONOSACCHARIDES
NUCLEI
NUCLEOTIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANS
PRIMATES
RADIOISOTOPES
REACTION KINETICS
SACCHARIDES
VERTEBRATES
551001* - Physiological Systems- Tracer Techniques