A stereospecific myo-inositol/D-chiro-inositol transporter in HepG2 liver cells. Identification with D-chiro-[3-3H]inositol

D-chiro-Inositol is an epimer of myo-inositol that is found in certain mammalian glycosylphosphatidylinositol protein anchors and inositol phosphoglycans possessing insulin-like bioactivity. In order to generate a probe for metabolic studies, D-chiro-[3-3H]inositol was synthesized by selective reduc...

Full description

Saved in:
Bibliographic Details
Published in:The Journal of biological chemistry 1996-04, Vol.271 (17), p.10073-10078
Main Authors: Ostlund, Jr, R E, Seemayer, R, Gupta, S, Kimmel, R, Ostlund, E L, Sherman, W R
Format: Article
Language:English
Subjects:
Binding, Competitive
Biological Transport - drug effects
Cytochalasin B - pharmacology
Humans
Inositol - chemistry
Inositol - metabolism
Kinetics
Liver - metabolism
Phlorhizin - pharmacology
Stereoisomerism
Tumor Cells, Cultured
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:D-chiro-Inositol is an epimer of myo-inositol that is found in certain mammalian glycosylphosphatidylinositol protein anchors and inositol phosphoglycans possessing insulin-like bioactivity. In order to generate a probe for metabolic studies, D-chiro-[3-3H]inositol was synthesized by selective reduction of D-chiro-3-inosose at pH 6.5 with sodium borotritide. D-chiro-[3-3H]Inositol was taken up by HepG2 human liver cells through a saturable and stereospecific pathway in which D-chiro-inositol and myo-inositol competed equally but L-chiro-inositol was not recognized. Dd-Glucose, but not L-glucose, competed for D-chiro-[3-3H]inositol uptake over glucose concentrations of 4-28 mM. Maximum transport capacity was 717 pmol/mg cell protein/3 h with a Km value of 348 microM. Uptake was reduced by 76% when sodium was eliminated from the medium and by 94% when the experiment was performed at 0 degrees C. The new myo/D-chiro-inositol transporter is distinct from the sodium-myo-inositol co-transporter found in many tissues and accounts for all of the saturable D-chiro-inositol uptake and for a portion of the saturable low affinity myo-inositol uptake in HepG2 cells. It may allow D-chiro-inositol to be used by cells in the presence of a relatively large amount of competing myo-inositol.
ISSN:0021-9258
DOI:10.1074/jbc.271.17.10073