Endurance training enhances lactate clearance during hyperlactatemia.
Constant infusions of cold molar lactate (178.0 +/- 1.6 mumol.kg-1.min-1), [U-14C]lactate (0.50 muCi/min), and [6-3H]glucose (0.5 muCi/min) were employed to study the effects of endurance training (running 1 h/day, at 38 m/min, 10% grade) on lactate clearance in resting, hyperlactatemic rats. Before infusion, resting blood lactate levels were not significantly different between controls, 1.10 +/- 0.04 mM, and trained animals, 1.16 +/- 0.04 mM. Lactate levels increased significantly during the infusion period, attaining steady-state mixed venous concentrations of 11.32 +/- 0.24 mM and 5.44 +/- 0.09 mM, respectively, for controls and trained animals. Lactate clearance rates, based on net lactate removal (i.e., not tracer-estimated lactate removal), were twofold greater in trained animals vs. controls, 33.0 +/- 0.7 and 15.4 +/- 0.4 ml.kg-1. min-1, respectively. Lactate specific activity values during the infusion period were not significantly different between controls, 22,243 +/- 236 dpm/mumol, and trained animals, 21,270 +/- 374 dpm/mumol, indicating similar endogenous dilution of the pyruvate-lactate pool. For both control and trained animals, essentially 100% of the 14C infused as lactate was recovered as either glucose or CO2; however, trained animals demonstrated a 25% greater rate of gluconeogenesis. At a given lactate production rate, trained animals maintain lower lactate levels through enhanced clearance via gluconeogenesis and oxidation.
Donovan
C M
CM
Department of Exercise Science, University of Southern California, Los Angeles 90089.
Pagliassotti
M J
MJ
D000818:Animals; D001639:Bicarbonates / Q000378:metabolism; D001786:Blood Glucose / Q000032:analysis; D002245:Carbon Dioxide / Q000378:metabolism; D005260:Female; D007773:Lactates / Q000097:blood / Q000378:metabolism* / Q000494:pharmacology; D019344:Lactic Acid; D009994:Osmolar Concentration; D010805:Physical Conditioning, Animal; D010807:Physical Endurance; D051381:Rats; D011919:Rats, Inbred Strains
D001639:Bicarbonates; D001786:Blood Glucose; D007773:Lactates; D002245:Carbon Dioxide; D019344:Lactic Acid