title: Increased [lactate] in working dog muscle reduces tension development independent of pH.
abstract: The purpose of this work was to examine the effect of the lactate ion on the fatigue process in working muscle independent of muscle [H+]. L-(+)-lactate was infused, at a pH that did not change arterial pH, into the blood perfusing an isolated, in situ dog gastrocnemius (N = 5) working at a submaximal intensity (isometric contractions at 2 Hz) and compared with control (C) conditions without lactate infusion. Each muscle was stimulated to work for two 60-min periods (separated by 45 min rest), consisting of three 20-min time periods with either the high arterial lactate condition (high [La]) or C condition sequentially ordered within each 60-min work period. Blood flow and O2 delivery were held constant between the C and high [La] conditions. Arterial and venous blood measurements and muscle biopsies were taken (7 biopsies from each condition) during each condition. Lactate infusion significantly increased arterial [La] (C = 4.2 +/- 0.2 mM vs high [La] = 14.4 +/- 0.2; mean +/- SE) and muscle [La] (C = 8.1 +/- 0.8 mM w.w. vs high [La] = 12.0 +/- 1.4) while arterial and muscle pH were unchanged between conditions. Muscle tension development was significantly reduced (C = 94 +/- 2 N.100 g-1 vs high [La] = 80 +/- 3) during lactate infusion and muscle O2 uptake changed proportionally with tension. These findings support an effect of the lactate anion on tension development which is independent of pH.
authors.affiliation: Department of Medicine, University of California, San Diego, La Jolla 92093-0623, USA.
authors.forename: M C
authors.initials: MC
authors.lastname: Hogan
authors.forename: L B
authors.initials: LB
authors.lastname: Gladden
authors.forename: S S
authors.initials: SS
authors.lastname: Kurdak
authors.forename: D C
authors.initials: DC
authors.lastname: Poole
mesh_terms: D000818:Animals; D004285:Dogs; D006863:Hydrogen-Ion Concentration; D007424:Intracellular Fluid / Q000378:metabolism; D007537:Isometric Contraction / Q000502:physiology*; D007773:Lactates / Q000097:blood / Q000493:pharmacokinetics*; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000098:blood supply / Q000378:metabolism*; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption / Q000502:physiology; D012039:Regional Blood Flow / Q000502:physiology
chemical_list: D007773:Lactates; D010100:Oxygen