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UPTAKE OF 3‐ O ‐METHYL‐ d ‐GLUCOSE INTO CULTURED HUMAN GLIOMA CELLS
Author(s) -
Edström A.,
Kanje M.,
Walum E.
Publication year - 1975
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1975.tb11893.x
Subject(s) - phloretin , phlorizin , cytochalasin b , glucose uptake , ouabain , population , chemistry , glucose transporter , medicine , biochemistry , endocrinology , microbiology and biotechnology , biophysics , biology , cell , sodium , insulin , environmental health , organic chemistry
— Human glioma cells (138 MG) were found to take up 3‐ O ‐methyl‐ d ‐glucose (3‐OMG) by a saturable low affinity transport system with a K m of 20 m m and a V max of 500 nmol/mg protein/min. About 20 per cent of the total uptake was due to passive diffusion. d ‐Glucose was a competitive inhibitor with a K i of 10 m m . Follow‐up experiments indicated that the same transport mechanism is involved in the uptake of n‐glucose and 3‐OMG. Phloretin (0·02 m m ) and cytochalasin B (0·002 m m ) strongly inhibited the uptake of 3‐OMG, whereas phlorizin (0·02 m m ), ouabain (0·1 m m ), NaCN (0·5 m m ) and iodoacetic acid (1·0 m m ) had no effect. The data suggest that 3‐OMG and d ‐glucose enter 138 MG cells mainly by a Na + ‐independent passive carrier‐mediated transport system. Serum‐deprivation doubled the population doubling time (T d ) without affecting the total uptake of 3‐OMG. An increase in the non‐specific (diffusional) uptake was balanced by a decrease in the specific (carrier‐medíated) uptake. After addition of dibutyryl cyclic AMP (dbcAMP, 0·25 m m ) the cells attained a morphology characteristic of differentiated glia cells. T d was maintained unchanged. The non‐specific uptake of 3‐OMG was not affected in cells grown in serum‐containing medium plus dbcAMP, whereas the specific uptake increased by 40 per cent and there‐fore also the total uptake. Similar, but more pronounced, changes were observed if serum‐deprived cells were treated with dbcAMP.