Glucose transport system in UMR-106-01 osteoblastic osteosarcoma cells: regulation by insulin.
Insulin is a potent stimulator of collagen synthesis and other osteoblastic cell functions. In various insulin-sensitive tissues, stimulation of glucose transport and glycolytic metabolism are hallmarks of insulin action and may play a role in insulin regulation of cellular function. However, the effects of insulin on glucose metabolism in osteoblast-like cells have not been defined. We therefore characterized 2-deoxy-D-glucose (2-DG) transport in UMR-106-01 rat osteoblastic osteosarcoma cells and examined its regulation by insulin. 2-DG (0.1 mM) uptake was shown to be linear with time over 45 minutes, temperature-sensitive, and inhibited by phloridzin. Competitive inhibition studies against other hexoses demonstrated a transport system stereospecificity for 2-DG similar to that previously demonstrated in fat and muscle cells. Kinetic analysis of 15 minute 2-DG uptake at 25 degrees C demonstrated a saturable transport mechanism with a Km (1.9 mM) similar to that observed for 2-DG transport in other tissues. Insulin stimulated 2-DG transport in a dose-related manner, with significant stimulation observed at 0.5 nM and maximal effect observed at 50 nM insulin. The stimulatory effect of insulin was reversibly inhibited by cytochalasin B (50 microM). Insulin stimulation of 2-DG transport was associated with a 1.7-fold increase in Vmax, while Km remained constant. When insulin effects on glucose transport were inhibited by the addition of 5 mM phloridzin, stimulatory effects on DNA and collagen synthesis were diminished, suggesting that stimulation of glucose transport may play a role in insulin effects on replication and function in osteoblast-like cells.
Ituarte
E A
EA
Department of Medicine, Wadsworth VA Medical Center, Los Angeles, CA 90073.
Halstead
L R
LR
Iida-Klein
A
A
Ituarte
H G
HG
Hahn
T J
TJ
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000503:physiopathology; D005947:Glucose / Q000378:metabolism / Q000493:pharmacokinetics*; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D010006:Osteoblasts / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D012516:Osteosarcoma / Q000378:metabolism* / Q000473:pathology / Q000648:ultrastructure; D010641:Phenotype; D051381:Rats; D014407:Tumor Cells, Cultured
D007328:Insulin; D005947:Glucose