title: Modulation of rat skeletal muscle microvascular O2 pressure via KATP channel inhibition following the onset of contractions.
abstract: Vascular hyperpolarization mediated, in part, by the ATP-sensitive K(+) (KATP) channel contributes to exercise-induced increases in skeletal muscle O2 delivery. We hypothesized that KATP channel inhibition via glibenclamide (GLI) would speed the fall of microvascular O2 driving pressure (PO2mv; set by the O2 delivery-O2 utilization ratio), during muscle contractions. Spinotrapezius muscle PO2mv (phosphorescence quenching) was measured in 12 adult Sprague Dawley rats during 180s of 1-Hz twitch contractions (∼ 6 V) under control and GLI (5mg/kg) conditions. The total mean PO2mv response time was greater with GLI (i.e., slowed; control: 42.0 ± 14.2, GLI: 79.5 ± 14.7s, p<0.05). A clear undershoot of the contracting steady-state PO2mv was evident with GLI (15.6 ± 5.3%, p<0.05) but not control (2.3 ± 1.6%, p>0.05). This indicates that KATP channel inhibition does not speed PO2mv kinetics per se during small muscle mass contraction. However, it does induce a transient mismatch of O2 delivery-O2 utilization, lowers PO2mv, and delays attainment of the contracting steady-state.
authors.affiliation: Department of Anatomy and Physiology, Kansas State University, Manhattan, KS 66506, USA. Electronic address: clark40@k-state.edu.
authors.forename: Clark T
authors.initials: CT
authors.lastname: Holdsworth
authors.affiliation: Department of Anatomy and Physiology, Kansas State University, Manhattan, KS 66506, USA.
authors.forename: Scott K
authors.initials: SK
authors.lastname: Ferguson
authors.affiliation: Department of Anatomy and Physiology, Kansas State University, Manhattan, KS 66506, USA; Department of Kinesiology, Kansas State University, Manhattan, KS 66506, USA.
authors.forename: David C
authors.initials: DC
authors.lastname: Poole
authors.affiliation: Department of Anatomy and Physiology, Kansas State University, Manhattan, KS 66506, USA; Department of Kinesiology, Kansas State University, Manhattan, KS 66506, USA.
authors.forename: Timothy I
authors.initials: TI
authors.lastname: Musch
mesh_terms: D000818:Animals; D005905:Glyburide / Q000494:pharmacology; D006439:Hemodynamics / Q000502:physiology; D054086:KATP Channels / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008297:Male; D055806:Microvessels / Q000187:drug effects / Q000502:physiology*; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D018482:Muscle, Skeletal / Q000098:blood supply / Q000187:drug effects / Q000502:physiology*; D009842:Oligopeptides; D010100:Oxygen / Q000378:metabolism*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D011312:Pressure; D017207:Rats, Sprague-Dawley; D012146:Rest / Q000502:physiology
chemical_list: D054086:KATP Channels; D009842:Oligopeptides; D026902:Potassium Channel Blockers; C048812:kinetensin; D010100:Oxygen; D005905:Glyburide
keywords: Conductance; Exercise hyperemia; Glibenclamide; Kinetics; O(2) delivery-to-utilization matching; Phosphorescence quenching