title: Glucose starvation is required for insulin stimulation of glucose uptake and metabolism in cultured microvascular endothelial cells.
abstract: In the present study we determined the uptake and disposition of glucose in serum-deprived rabbit coronary microvessel endothelial (RCME) cells. RCME cells exhibited stereospecific hexose uptake inhibited by cytochalasin B. Pretreatment of the RCME cells with potassium cyanide or 2,4-dinitrophenol inhibited 2-deoxyglucose uptake but not 3-O-methylglucose transport. A major proportion (30-60%) of the 2-deoxyglucose present in the RCME cells was not phosphorylated. These two observations suggested that the rate-limiting step in the uptake of 2-deoxyglucose was not transport but rather the phosphorylation of 2-deoxyglucose to 2-deoxyglucose 6-phosphate. When glucose-deprived cells were incubated 2 hr with [U-14C]glucose the disposition of the label was as follows: glycogen 60%, acid-soluble fraction 30%, and lipid less than 5%. In contrast glucose-fed cells exhibited lower overall glucose incorporation, and a slightly different disposition: glycogen 45%, acid-soluble fraction 50%, and lipid 5%. Glucose-deprived RCME cells also exhibited greater basal levels of 2-deoxyglucose uptake compared to glucose-fed cells. RCME cells incubated in the absence of glucose and serum for 16 hr exhibited dose-dependent insulin stimulation of hexose uptake and subsequent metabolism to macromolecules (i.e., glycogen and the acid-soluble fraction). Significant effects of insulin were observed with concentrations as low as 2 x 10(-10) M, well within the physiological range. In contrast, cells preincubated in serum-free culture medium containing 5.5 mM glucose did not exhibit insulin-enhanced hexose uptake or glucose metabolism (even at doses as high as 10(-7) M). These studies indicate that the effects of insulin on rabbit coronary microvascular endothelial cell glucose uptake and metabolism require both serum and glucose deprivation.
authors.affiliation: Department of Physiology, New York Medical College, Valhalla 10595.
authors.forename: M E
authors.initials: ME
authors.lastname: Gerritsen
authors.forename: T M
authors.initials: TM
authors.lastname: Burke
authors.forename: L A
authors.initials: LA
authors.lastname: Allen
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D002250:Carbon Radioisotopes; D002478:Cells, Cultured; D003571:Cytochalasin B / Q000494:pharmacology; D003847:Deoxyglucose / Q000378:metabolism / Q000493:pharmacokinetics; D004140:Dinitrophenols / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000166:cytology / Q000000981:diagnostic imaging; D005947:Glucose / Q000172:deficiency / Q000378:metabolism* / Q000493:pharmacokinetics; D006003:Glycogen / Q000032:analysis; D006601:Hexoses / Q000378:metabolism / Q000493:pharmacokinetics; D007328:Insulin / Q000493:pharmacokinetics / Q000494:pharmacology*; D008055:Lipids / Q000032:analysis; D008833:Microcirculation / Q000166:cytology; D010042:Ouabain / Q000494:pharmacology; D011190:Potassium Cyanide / Q000494:pharmacology; D011817:Rabbits; D011877:Radionuclide Imaging; D012588:Scintillation Counting
chemical_list: D001786:Blood Glucose; D002250:Carbon Radioisotopes; D004140:Dinitrophenols; D006601:Hexoses; D007328:Insulin; D008055:Lipids; D003571:Cytochalasin B; D010042:Ouabain; D006003:Glycogen; D003847:Deoxyglucose; D005947:Glucose; D011190:Potassium Cyanide