Respective oxidation of lactate and glucose ingested simultaneously
during exercise using 13c-labeling.
P[acute]eronnet, F., Y. Burelle, D. Massicotte, C. Lavoie, and C.
Hillaire-Marcel.
D[acute]epartement d'[acute]education physique, Universit[acute]e
de Montr[acute]eal, CP 6128 Centre Ville, Montr[acute]eal, P.Q.
Canada
APStracts 3:0492A, 1996.
The purpose of this experiment was to measure the oxidation rate of
exogenous lactate (25 g, as Na+, K+, Ca++ and Mg++ salts) and glucose
(75 g) ingested simultaneously (in 1000 mL of water) during prolonged
exercise (120 min, 65 +/- 3 % VO2max in 6 male subjects) using 13C
-labeling. The percentage of exogenous glucose and lactate oxidized
were similar (48 +/- 3 % vs 45 +/- 5 % respectively), however,
because of the small amount of oral lactate which could be tolerated
without gastro-intestinal discomfort, the amount of exogenous lactate
oxidized was much smaller than that of exogenous glucose (11.1 +/-
0.5 vs 36.3 +/- 1.3 g respectively) and contributed to only 2.6 +/-
0.4 % to the energy yield (vs 8.4 +/- 1.9 % for exogenous glucose).
The cumulative amount of exogenous glucose and lactate oxidized was
similar to that observed when 100 g of 13C-glucose were ingested
(47.3 +/- 1.8 vs 50.9 +/- 1.2 g respectively). When 13C-glucose was
ingested, changes in plasma glucose 13C/12C indicated that between 39
and 61 % of plasma glucose derived from exogenous glucose. On the
other hand, plasma glucose13C/12C remained unchanged when 13C-lactate
was ingested, suggesting no prior conversion into glucose before
oxidation.
Received 29 May 1996; accepted in final form 21 October 1996.
APS Manuscript Number A507-6.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 13 November 1996