title: Exercise-stimulated glucose transport in skeletal muscle is nitric oxide dependent.
abstract: It has been suggested that there are separate insulin-stimulated and contraction-stimulated glucose transport pathways in skeletal muscle. This study examined the effects of nitric oxide on glucose transport in rat skeletal muscle by use of an isolated sarcolemmal membrane preparation and the nitric oxide synthase inhibitor N omega-nitro-L-arginine methyl ester (L-NAME), administered in the drinking water (1 mg/ml). Female Sprague-Dawley rats were divided into five groups: control, acute exercise, acute exercise+L-NAME, insulin stimulated, and insulin stimulated+L-NAME. Exercise (45 min of exhaustive treadmill running) increased glucose transport (37 +/- 2 to 76 +/- 5 pmol.mg-1.15 s-1) and this increase was completely inhibited by L-NAME (40 +/- 4 pmol.mg-1.15 s-1). A maximum dose of insulin increased glucose transport (87 +/- 10 pmol.mg-1.15 s-1), and adding L-NAME had no effect (87 +/- 11 pmol.mg-1.15 s-1). In addition, exercise, but not exercise+L-NAME, increased sarcolemma GLUT-4 content. This study confirms that there are separate pathways for contraction- and insulin-stimulated glucose transport. More importantly, although exercise and insulin both significantly increased glucose transport, L-NAME had no effect on insulin-stimulated glucose transport but blocked the exercise-stimulated transport. We conclude that nitric oxide is involved in the signal transduction mechanism to increase glucose transport during exercise.
authors.affiliation: Department of Physiological Science, University of California, Los Angeles 90024, USA.
authors.forename: C K
authors.initials: CK
authors.lastname: Roberts
authors.forename: R J
authors.initials: RJ
authors.lastname: Barnard
authors.forename: S H
authors.initials: SH
authors.lastname: Scheck
authors.forename: T W
authors.initials: TW
authors.lastname: Balon
mesh_terms: D000284:Administration, Oral; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D005080:Exercise Test; D005260:Female; D005947:Glucose / Q000378:metabolism*; D051275:Glucose Transporter Type 4; D007328:Insulin / Q000494:pharmacology*; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D009119:Muscle Contraction / Q000502:physiology*; D009124:Muscle Proteins; D018482:Muscle, Skeletal / Q000187:drug effects / Q000502:physiology*; D019331:NG-Nitroarginine Methyl Ester / Q000008:administration & dosage / Q000494:pharmacology*; D005082:Physical Exertion / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values; D012508:Sarcolemma / Q000378:metabolism
chemical_list: D051275:Glucose Transporter Type 4; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C495694:Slc2a4 protein, rat; D005947:Glucose; D019331:NG-Nitroarginine Methyl Ester