title: Magnesium and calcium effects on uptake of hexoses and uridine by chick embryo fibroblasts.
abstract: Cultures of chick embryo fibroblasts were incubated for varying periods in media containing different concentrations of Ca2+ and Mg2+-Mg2+ deprivation produced a gradual decrease in the Vmax of the glucose transport system for the D-glucose analogues 3-O-[3H]methyl-D-glucose and 2-deoxy-D-[3H]glucose and a parallel decrease in the rate of production of lactate from glucose in the medium. It greatly reduced the rates of [3H]uridine uptake and incorporation by decreasing the Vmax of the uridine transport system. Addition of Mg2+ to Mg2+-deprived cultures rapidly increased the rate of [3H]uridine uptake without requiring protein synthesis and increased the rate of 2-deoxy-D-[3H]glucose uptake without requiring RNA synthesis. These effects of changes in Mg2+ concentration qualitatively reproduce the effects of such variables as cell density and serum and insulin concentrations. Ca2+ deprivation resulted in similar, though much smaller, changes in the activities of the two transport systems, but also greatly increased the "leakiness" of the cells to the nontransported hexose L-[3H]glucose.
mesh_terms: D000818:Animals; D001693:Biological Transport, Active; D002118:Calcium / Q000494:pharmacology*; D002642:Chick Embryo; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D003837:Deoxy Sugars / Q000378:metabolism*; D003847:Deoxyglucose / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology*; D008757:Methylglucosides / Q000378:metabolism*; D008759:Methylglycosides / Q000378:metabolism*; D011691:Puromycin / Q000494:pharmacology; D014529:Uridine / Q000378:metabolism*
chemical_list: D003837:Deoxy Sugars; D008757:Methylglucosides; D008759:Methylglycosides; D003609:Dactinomycin; D011691:Puromycin; D003513:Cycloheximide; D003847:Deoxyglucose; D008274:Magnesium; D002118:Calcium; D014529:Uridine
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