AJP - Endocrinology and Metabolism, Vol 257, Issue 5 E782-E789, Copyright © 1989 by American Physiological Society

ARTICLES

Endurance training enhances lactate clearance during hyperlactatemia

C. M. Donovan and M. J. Pagliassotti
Department of Exercise Science, University of Southern California, Los Angeles 90089.

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.

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