Short-term training increases human muscle mct1 and femoral venous
lacate in relation to muscle lactate.
Bonen, A., K. J. A. McCullagh, C. T. Putman, E. Hultman, N. L. Jones,
G. J. F. Heigenhauser.
Department of Kinesiology, University of Waterloo, Waterloo,
Ontario N2L 3G1, The Karolinska Institute, S-141 Stockholm 86,
Sweden, Department of Medicine, McMaster University Medical Centre,
Hamilton, Ontario, Canada L8N 3Z5
APStracts 4:0223E, 1997.
We examined the effects of increasing a known lactate transporter
protein, monocarboxylate transporter 1 (MCT1), on lactate extrusion
from human skeletal muscle during exercise. Before and after short
term bicycle ergometry training (2 h/day, 7 days at 65% VO2 max) the
subjects (N = 7) completed a continuous bicycle ergometer ride at 30%
VO2max (20min), 60% VO2max (20min) and 75% VO2max (20min). Muscle
biopsy samples (vastus lateralis), and arterial and femoral venous
blood samples were obtained before exercise and at the end of each
work load. After 7 days of training the MCT1 content in muscle was
increased (+18%; P<0.05). The concentrations of both muscle lactate
and femoral venous lactate were reduced during exercise (P<0.05)
that was performed after training. High correlations were observed
between muscle lactate and venous lactate before training (r =0.92, P
<0.05) and after training (r =0.85, P <0.05), but, the slopes of
the regression lines between these variables differed markedly.
Before training the slope was 0.12 +/- 0.01 (mM lactate/mmol
lactate.kg-1 muscle dry wt) and this was increased by 33 % after
training to 0.18 +/- 0.02 (mM lactate/mmol lactate.kg-1 muscle dry
wt). This indicated that after training the femoral venous lactate
concentrations were increased for a given amount of muscle lactate.
These results suggest that lactate extrusion from exercising muscles
is increased after training, and this may be associated with the
increase in skeletal muscle MCT1.
Received 29 April 1997; accepted in final form 1 October 1997.
APS Manuscript Number E197-7.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 29 October 1997