title: Contraction-induced intracellular signals and their relationship to muscle GLUT-4 concentration.
abstract: This investigation used a model of increased skeletal muscle contractile activity to evaluate whether the adenylate cyclase-adenosine 3',5'-cyclic monophosphate (cAMP) pathway and/or the high-energy phosphate state of the muscle might be temporally related to the contraction-induced increase in skeletal muscle GLUT-4 protein concentration. Plantaris and gastrocnemius muscles of Sprague-Dawley rats were subjected to 3, 7, 14, or 28 days of chronic low-frequency electrical stimulation (10 Hz, 24 h/day). GLUT-4 protein concentration was slightly reduced after 3 days of electrical stimulation, similar to control values at 7 days and significantly elevated above control at 14 days (53%, P < 0.05) and 28 days (338%, P < 0.05) of stimulation. ATP, creatine phosphate, creatine, and P, were inversely related to GLUT-4 protein concentration. Adenylate cyclase activity increased with electrical stimulation and was significantly related to the increased GLUT-4 protein. cAMP was significantly increased at 14 days of stimulation and remained elevated through 28 days. These results demonstrate that both the adenylate cyclase-cAMP pathway and the high-energy phosphate state of the muscle are temporally related to elevations in skeletal muscle GLUT-4 protein concentration in response to chronic low-frequency electrical stimulation and, as such, suggest that both may comprise a component of the intracellular signal that regulates the contraction-induced increase in skeletal muscle GLUT-4 protein concentration.
authors.affiliation: Department of Kinesiology, University of Texas at Austin 78712, USA.
authors.forename: B B
authors.initials: BB
authors.lastname: Yaspelkis
authors.forename: A L
authors.initials: AL
authors.lastname: Castle
authors.forename: R P
authors.initials: RP
authors.lastname: Farrar
authors.forename: J L
authors.initials: JL
authors.lastname: Ivy
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D001835:Body Weight; D000242:Cyclic AMP / Q000378:metabolism; D004734:Energy Metabolism; D005260:Female; D051275:Glucose Transporter Type 4; D007425:Intracellular Membranes / Q000502:physiology*; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009119:Muscle Contraction / Q000502:physiology*; D009124:Muscle Proteins; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000378:metabolism*; D009929:Organ Size; D009994:Osmolar Concentration; D010710:Phosphates / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction
chemical_list: D051275:Glucose Transporter Type 4; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D010710:Phosphates; C495694:Slc2a4 protein, rat; D000242:Cyclic AMP; D000262:Adenylyl Cyclases