title: Regulation of hexose transport in BALB/c 3T3 preadipose cells: effects of glucose concentration and 12-O-tetradecanoylphorbol-13-acetate.
abstract: Like many cell types in culture, both undifferentiated and differentiated BALB/c 3T3 preadipose cells respond to glucose deprivation with an increased uptake of 2-deoxy-D-glucose (deoxyglucose) and 3-O-methyl-D-glucose (methylglucose). Glucose readdition to glucose-deprived cultures resulted in a prompt fall in uptake activity; in undifferentiated cells, a half-maximally effective concentration of glucose was approximately 0.5 mM, while 0.1 mM was ineffective. Several hexoses differed in their efficacy of "deactivating" methylglucose transport in glucose-deprived cells; it appeared that a particular hexose must be metabolized beyond the 6-phosphate form to deactivate the transport system. Previous studies have shown that the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) stimulates hexose transport in undifferentiated and differentiated BALB/c 3T3 cells. In this study, it was found that TPA (and insulin in differentiated cells) prevented the glucose-induced deactivation of transport activity. Glucose-induced deactivation of transport activity was also prevented by cycloheximide or actinomycin D addition concomitantly with glucose. In glucose-starved cells, agents such as TPA and insulin appear to override a cellular control mechanism sensitive to the external concentration of glucose, so that elevated levels of transport activity are maintained under environmental conditions (i.e., a return to physiological glucose concentrations) that normally induce a fall in transport activity.
mesh_terms: D019325:3-O-Methylglucose; D000818:Animals; D001692:Biological Transport; D002460:Cell Line; D003837:Deoxy Sugars / Q000378:metabolism*; D003847:Deoxyglucose / Q000378:metabolism*; D005632:Fructose / Q000494:pharmacology; D005944:Glucosamine / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology*; D007328:Insulin / Q000494:pharmacology; D007700:Kinetics; D008358:Mannose / Q000494:pharmacology; D008757:Methylglucosides / Q000378:metabolism*; D008759:Methylglycosides / Q000378:metabolism*; D051379:Mice; D010704:Phorbols / Q000494:pharmacology*; D014176:Protein Biosynthesis; D012313:RNA / Q000096:biosynthesis; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
chemical_list: D003837:Deoxy Sugars; D007328:Insulin; D008757:Methylglucosides; D008759:Methylglycosides; D010704:Phorbols; D019325:3-O-Methylglucose; D005632:Fructose; D012313:RNA; D003847:Deoxyglucose; D005947:Glucose; D005944:Glucosamine; D013755:Tetradecanoylphorbol Acetate; D008358:Mannose