title: Coordinate regulation of glucose transporter function, number, and gene expression by insulin and sulfonylureas in L6 rat skeletal muscle cells.
abstract: The extrapancreatic actions of sulfonylureas on the glucose transport system were studied in the L6 line of cultured rat skeletal muscle cells. Insulin (10(-7) M) increased 2-deoxyglucose uptake in differentiated L6 myotubes by 30-40% after 8 h of incubation. The sulfonylurea tolazamide (0.6 mg/ml, 22 h) had no effect on glucose uptake in the absence of insulin, but increased insulin-stimulated 2-deoxyglucose uptake twofold. The total cellular content of glucose transporters was assessed with a monoclonal anti-transporter antibody by a solid-phase ELISA method. Insulin (8 h) increased the quantity of glucose transporters, with a maximal twofold increase at 10(-7) M and a dose-response curve similar to that for insulin stimulation of glucose uptake. In spite of its lack of effect on glucose uptake, tolazamide alone (0.6 mg/ml) increased the cellular content of transporters by 70%. The effects of insulin and tolazamide on transporter gene expression were studied with probes derived from Hep G2 glucose transporter cDNA. Insulin increased the transporter mRNA level 1.7-fold, tolazamide increased it 1.5-fold, and the combination of insulin and tolazamide increased transporter mRNA 3-fold. It is concluded that sulfonylureas, together with insulin, enhance glucose uptake in L6 skeletal muscle cells by increasing the number of functioning glucose transport molecules. The long-term regulation of the glucose transport system in skeletal muscle by insulin and sulfonylureas in vivo may involve similar changes in transporter function, number, and gene expression.
authors.affiliation: Joslin Diabetes Center, Boston, Massachusetts 02215.
authors.forename: P H
authors.initials: PH
authors.lastname: Wang
authors.forename: D
authors.initials: D
authors.lastname: Moller
authors.forename: J S
authors.initials: JS
authors.lastname: Flier
authors.forename: R C
authors.initials: RC
authors.lastname: Nayak
authors.forename: R J
authors.initials: RJ
authors.lastname: Smith
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000032:analysis; D015152:Blotting, Northern; D015153:Blotting, Western; D002478:Cells, Cultured; D004247:DNA; D015342:DNA Probes; D003847:Deoxyglucose / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D005786:Gene Expression Regulation; D007328:Insulin / Q000494:pharmacology*; D009004:Monosaccharide Transport Proteins / Q000235:genetics* / Q000502:physiology; D009132:Muscles / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D014042:Tolazamide / Q000494:pharmacology*
chemical_list: D000911:Antibodies, Monoclonal; D015342:DNA Probes; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D012333:RNA, Messenger; D004247:DNA; D003847:Deoxyglucose; D014042:Tolazamide