Skeletal muscle pyruvate dehydrogenase activity during maximal
exercise in humans.
Putman, C. T., N. L. Jones, L. C. Lands, T. M. Bragg, M. G. Hollidge
-Horvat, and G. J. F. Heigenhauser.
Department of Medicine, McMaster University Medical Centre,
Hamilton, Ontario, CANADA L8N 3Z5
APStracts 2:0081E, 1995.
The regulation of the active form of pyruvate dehydrogenase (PDHa) and
related metabolic events were examined in human skeletal muscle
during repeated bouts of maximum exercise. Seven subjects completed 3
consecutive 30 second bouts of maximum isokinetic cycling, separated
by 4 min of recovery. Biopsies of the vastus lateralis were taken
before and immediately after each bout. PDHa increased from 0.45+/
-0.15 to 2.96+/-0.38; from 1.10+/-0.11 to 2.91+/-0.11 and from 1.28+/
-0.18 to 2.82+/-0.32 mmol.min-1.kg ww-1 during bouts 1, 2 and 3
respectively. Glycolytic flux was 13 fold greater than PDHa in bouts
1 and 2, and 4 fold greater during bout 3. This discrepancy between
the rate of pyruvate production and oxidation resulted in substantial
lactate accumulation to 89.5+/-11.6 in bout 1, 130.8+/-13.8 in bout 2
and 106.6+/-10.1 mmol.kg dw-1 in bout 3. These events coincided with
an increase in the mitochondrial oxidation state, as reflected in a
fall in the mitochondrial NADH-to-NAD ratio, indicating that muscle
lactate production during exercise was not an O2 dependent process in
our subjects. During exercise the primary factor regulating PDHa
transformation was probably intracellular Ca2+. In contrast, the
primary regulatory factors causing greater PDHa during recovery were
lower ATP-to-ADP and NADH-to-NAD ratios, and increased concentrations
of pyruvate and H+. Greater PDHa during recovery facilitated
continued oxidation of the lactate load between exercise bouts.
Received 23 February 1994; accepted in final form 12 April 1995.
APS Manuscript Number E86-5.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 25 April 1995.