title: IGF-I measurement across blood, interstitial fluid, and muscle biocompartments following explosive, high-power exercise.
abstract: Insulin-like growth factor-I (IGF-I) resides across different biocompartments [blood, interstitial fluid (ISF), and muscle]. Whether circulating IGF-I responses to exercise reflect local events remains uncertain. We measured the IGF-I response to plyometric exercise across blood, ISF, and muscle biopsy from the vastus lateralis. Twenty volunteers (8 men, 12 women, 22 ± 1 yr) performed 10 sets of 10 plyometric jump repetitions at a 40% 1-repetition maximum. Blood, ISF, and muscle samples were taken pre- and postexercise. Circulating IGF-I increased postexercise: total IGF-I (preexercise = 546 ± 42, midexercise = 585 ± 43, postexercise = 597 ± 45, +30 = 557 ± 42, +60 = 536 ± 40, +120 = 567 ± 42 ng/ml; midexercise, postexercise, and +120 greater than preexercise, P < 0.05); Free IGF-I (preexercise = 0.83 ± 0.09, midexercise = 0.78 ± 0.10, postexercise = 0.79 ± 0.11, +30 = 0.93 ± 0.10, +60 = 0.88 ± 0.10, + 120 = 0.91 ± 0.11 ng/ml; +30 greater than all other preceding time points, P < 0.05). No exercise-induced changes were observed for ISF IGF-I (preexercise = 2.35 ± 0.29, postexercise = 2.46 ± 0.35 ng/ml). No changes were observed for skeletal muscle IGF-I protein, although IGF-I mRNA content increased ∼40% postexercise. The increase in circulating total and free IGF-I was not correlated with increases in ISF IGF-I or muscle IGF-I protein content. Our data indicate that exercise-induced increases in circulating IGF-I are not reflective of local IGF-I signaling.
authors.affiliation: Military Performance Division, The United States Army Research Institute of Environmental Medicine, Natick, Massachusetts, USA. bradley.nindl@us.army.mil
authors.forename: Bradley C
authors.initials: BC
authors.lastname: Nindl
authors.forename: Maria L
authors.initials: ML
authors.lastname: Urso
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Pierce
authors.forename: Dennis E
authors.initials: DE
authors.lastname: Scofield
authors.forename: Brian R
authors.initials: BR
authors.lastname: Barnes
authors.forename: William J
authors.initials: WJ
authors.lastname: Kraemer
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Anderson
authors.forename: Carl M
authors.initials: CM
authors.lastname: Maresh
authors.forename: Kathleen N
authors.initials: KN
authors.lastname: Beasley
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Zambraski
mesh_terms: D015444:Exercise / Q000502:physiology*; D045604:Extracellular Fluid / Q000737:chemistry*; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors; D055815:Young Adult
chemical_list: D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I