title: Increased flow rate and papaverine increase K+ exchange in perfused rat hind-limb skeletal muscle.
abstract: This study tested the hypothesis that increases in perfusate flow rate result in increased rates of unidirectional and net K+ transport in rat hind-limb skeletal muscle at rest. Ten neurally and vascularly isolated hind limbs, with arterial and venous catheters placed proximal to the popliteal region, were perfused for 10-min periods at flow rates (presented in a random order) of 0.27, 0.42, 0.63, 0.84, or 1.05 mL x min(-1) x g(-1). Potassium extraction and unidirectional K+ influx were determined using 42K, and arterial perfusion pressure was measured continuously. Increases in flow rate resulted in decreases in K+ extraction and increases in unidirectional K+ influx, unidirectional K+ efflux, and net K+ efflux. The increases in K+ flux were associated with increases in oxygen uptake, glucose uptake, and lactate release. In separate experiments (n = 5), the vasodilator papaverine (10(-4) M) did not further vasodilate the vasculature of resting hind limbs, suggesting that the hind limbs in this preparation were fully vasodilated. Papaverine, at constant flow, resulted in a nearly 1.5-fold increase in K+ extraction, a doubling of unidirectional K+ influx, and increases in unidirectional K+ efflux and net K+ efflux. It is concluded that physiological increases in flow rate result in increases in K+ transport in isolated, perfused rat hind-limb skeletal muscle. Furthermore, papaverine appeared to induce an increase in skeletal muscle membrane permeability to K+.
authors.affiliation: Department of Human Biology and Nutritional Sciences, University of Guelph, ON, Canada. mLindinger.ns@aps.uoguelph.ca
authors.forename: M I
authors.initials: MI
authors.lastname: Lindinger
authors.forename: T J
authors.initials: TJ
authors.lastname: Hawke
mesh_terms: D000818:Animals; D005947:Glucose / Q000378:metabolism; D006614:Hindlimb; D017136:Ion Transport / Q000187:drug effects; D019344:Lactic Acid / Q000378:metabolism; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply / Q000378:metabolism*; D010208:Papaverine / Q000494:pharmacology*; D010477:Perfusion; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012039:Regional Blood Flow; D014655:Vascular Resistance; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: D014665:Vasodilator Agents; D019344:Lactic Acid; D010208:Papaverine; D005947:Glucose; D011188:Potassium