title: Beta-adrenergic receptors are not responsible for exercise stimulation of glucose transport.
abstract: This study was designed to examine whether the increased glucose transport after acute exercise in rat skeletal muscle is mediated via beta-adrenergic receptor stimulation. Sarcolemmal (SL) membranes were isolated from three groups: control (C), acute exercise (E), and exercise + propranolol (E+P). The acute exercise bout was performed on a treadmill and consisted of a 45-min run until near exhaustion. E+P received an intravenous propranolol injection (0.8 mg/kg) 10 min before the exercise session. Michaelis-Menten kinetics at 1.5 s indicated that the Vmax for glucose transport was increased after each perturbation compared with C but were not different from each other (E, 4,334 +/- 377; E+P, 4,824 +/- 357; and C, 1,366 +/- 124 pmol.mg protein-1.s-1). The apparent Km's were similar in all groups. Scatchard plots for the D-glucose inhibitable class of cytochalasin B binding sites indicated no differences in either the total number of binding sites in the SL vesicles (C, 5.5 +/- 0.3; E, 5.1 +/- 0.2, and E+P, 5.1 +/- 0.3 pmol/mg protein) or in their dissociation constant (Kd) (C, 46 +/- 3; E, 48 +/- 3; and E+P, 49 +/- 2 nM). The increase in Vmax for transport was similar between E and E+P, indicating that exercise does not stimulate glucose transport via the beta-adrenergic receptor.
authors.affiliation: Department of Kinesiology, University of California, Los Angeles 90024.
authors.forename: E
authors.initials: E
authors.lastname: Sternlicht
authors.forename: R J
authors.initials: RJ
authors.lastname: Barnard
authors.forename: G K
authors.initials: GK
authors.lastname: Grimditch
mesh_terms: D000818:Animals; D003571:Cytochalasin B / Q000378:metabolism; D005260:Female; D005947:Glucose / Q000378:metabolism*; D006003:Glycogen / Q000378:metabolism; D007700:Kinetics; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009132:Muscles / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D005082:Physical Exertion; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D012016:Reference Values; D012508:Sarcolemma / Q000378:metabolism*
chemical_list: D009004:Monosaccharide Transport Proteins; D011943:Receptors, Adrenergic, beta; D003571:Cytochalasin B; D006003:Glycogen; D011433:Propranolol; D005947:Glucose