title: Effects of prior exercise on the action of insulin-like growth factor I in skeletal muscle.
abstract: Prior exercise increases insulin sensitivity for glucose and system A neutral amino acid transport activities in skeletal muscle. Insulin-like growth factor I (IGF-I) also activates these transport processes in resting muscle. It is not known, however, whether prior exercise increases IGF-I action in muscle. Therefore we determined the effect of a single exhausting bout of swim exercise on IGF-I-stimulated glucose transport activity [assessed by 2-deoxy-D-glucose (2-DG) uptake] and system A activity [assessed by alpha-(methylamino)isobutyric acid (MeAIB) uptake] in the isolated rat epitrochlearis muscle. When measured 3.5 h after exercise, the responses to a submaximal concentration (0.2 nM), but not a maximal concentration (13.3 nM), of insulin for activation of 2-DG uptake and MeAIB uptake were enhanced. In contrast, prior exercise increased markedly both the submaximal (5 nM) and maximal (20 nM) responses to IGF-I for activation of 2-DG uptake, whereas only the submaximal response to IGF-I (3 nM) for MeAIB uptake was enhanced after exercise. We conclude that 1) prior exercise significantly enhances the response to a submaximal concentration of IGF-I for activation of the glucose transport and system A neutral amino acid transport systems in skeletal muscle and 2) the enhanced maximal response for IGF-I action after exercise is restricted to the signaling pathway for activation of the glucose transport system.
authors.affiliation: Department of Exercise and Sport Sciences, University of Arizona, Tucson 85721.
authors.forename: E J
authors.initials: EJ
authors.lastname: Henriksen
authors.forename: L L
authors.initials: LL
authors.lastname: Louters
authors.forename: C S
authors.initials: CS
authors.lastname: Stump
authors.forename: C M
authors.initials: CM
authors.lastname: Tipton
mesh_terms: D000621:Aminoisobutyric Acids / Q000493:pharmacokinetics; D000818:Animals; D003847:Deoxyglucose / Q000493:pharmacokinetics; D007328:Insulin / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D008297:Male; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D009132:Muscles / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D005082:Physical Exertion; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D000621:Aminoisobutyric Acids; D007328:Insulin; D009004:Monosaccharide Transport Proteins; C017911:2-(methylamino)isobutyric acid; D007334:Insulin-Like Growth Factor I; D003847:Deoxyglucose