title: VO(2) on-kinetics in isolated canine muscle in situ during slowed convective O(2) delivery.
abstract: The purpose of this study was to examine O(2) uptake (Vo(2)) on-kinetics when the spontaneous blood flow (and therefore O(2) delivery) on-response was slowed by 25 and 50 s. The isolated gastrocnemius muscle complex (GS) in situ was studied in six anesthetized dogs during transitions from rest to a submaximal metabolic rate (≈50-70% of peak Vo(2)). Four trials were performed: 1) a pretrial in which resting and steady-state blood flows were established, 2) a control trial in which the blood flow on-kinetics mean response time (MRT) was set at 20 s (CT20), 3) an experimental trial in which the blood flow on-kinetics MRT was set at 45 s (EX45), and 4) an experimental trial in which the blood flow on-kinetics MRT was set at 70 s (EX70). Slowing O(2) delivery via slowing blood flow on-kinetics resulted in a linear slowing of the Vo(2) on-kinetics response (R = 0.96). Average MRT values for CT20, EX45, and EX70 Vo(2) on-kinetics were (means ± SD) 17 ± 2, 23 ± 4, and 26 ± 3 s, respectively (P < 0.05 among all). During these transitions, slowing blood flow resulted in greater muscle deoxygenation (as indicated by near-infrared spectroscopy), suggesting that lower intracellular Po(2) values were reached. In this oxidative muscle, Vo(2) and O(2) delivery were closely matched during the transition period from rest to steady-state contractions. In conjunction with our previous work showing that speeding O(2) delivery did not alter Vo(2) on-kinetics under similar conditions, it appears that spontaneously perfused skeletal muscle operates at the nexus of sufficient and insufficient O(2) delivery in the transition from rest to contractions.
authors: Department of Kinesiology, Auburn University, Auburn, Alabama, USA. matthewlgoodwin@gmail.com
authors: Matthew L
authors: ML
authors: Goodwin
authors: Andrés
authors: A
authors: Hernández
authors: Nicola
authors: N
authors: Lai
authors: Marco E
authors: ME
authors: Cabrera
authors: L Bruce
authors: LB
authors: Gladden
mesh_terms: D000818:Animals; D004285:Dogs; D005260:Female; D007700:Kinetics; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology*; D012039:Regional Blood Flow / Q000502:physiology; D019265:Spectroscopy, Near-Infrared / Q000379:methods; D013997:Time Factors
chemical_list: D010100:Oxygen