title: Stimulation-enhanced 3-O-methylglucose efflux from the frog sartorius: kinetics and properties of the system.
abstract: The characteristics of the process by which contraction enhances glucose transport in the frog sartorius were studied. Electrical stimulation increased the permeability of muscles to 3-O-methylglucose (3-O-MeGlc), a nonmetabolizable glucose analogue, increasing efflux as well as uptake. Enhanced efflux was due to an increase in Vmax of the efflux process. A lactacidosis had no effect on basal 3-O-MeGlc efflux, and replacement of media Na+ with Li+ did not affect stimulation-induced uptake. Also, basal and stimulated uptake was not affected by 1 microM 12-O-tetradecanoylphorbol-13-acetate (TPA), a protein kinase C activator. Lastly, N-carbobenzoxy-glycyl-L-phenylalaninamide, which inhibits insulin-enhanced, but not basal, glucose uptake in adipocytes, inhibited both basal and stimulated 3-O-MeGlc fluxes in the frog sartorius. From these findings, we conclude: (1) contraction and exercise enhance glucose transport in muscle by increasing the number of transporters in the plasma membrane, or their turnover, by an unknown process; and (2) basal glucose transport of muscle, unlike that of adipocytes, can not be distinguished from stimulated transport on the basis of its insensitivity to N-carbobenzoxyglycyl-L-phenylalaninamide.
authors.affiliation: Department of Pharmacology, Thomas Jefferson University, Philadelphia, PA.
authors.forename: G W
authors.initials: GW
authors.lastname: Booz
authors.forename: C P
authors.initials: CP
authors.lastname: Bianchi
mesh_terms: D019325:3-O-Methylglucose; D000818:Animals; D002118:Calcium / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D004151:Dipeptides / Q000494:pharmacology; D004558:Electric Stimulation; D006801:Humans; D007700:Kinetics; D007976:Leupeptins / Q000494:pharmacology; D008297:Male; D008757:Methylglucosides / Q000378:metabolism*; D009132:Muscles / Q000378:metabolism* / Q000502:physiology; D010693:Phloretin / Q000494:pharmacology; D011894:Rana pipiens; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D004151:Dipeptides; D007976:Leupeptins; D008757:Methylglucosides; C019156:carbobenzoxyglycylphenylalanine; D019325:3-O-Methylglucose; D003513:Cycloheximide; C032854:leupeptin; D013755:Tetradecanoylphorbol Acetate; D010693:Phloretin; D002118:Calcium