AJP - Endocrinology and Metabolism, Vol 270, Issue 3 E400-E406, Copyright © 1996 by American Physiological Society
Metabolic responses of canine gracilis muscle during contraction with partial ischemia
J. A. Timmons, S. M. Poucher, D. Constantin-Teodosiu, V. Worrall, I. A. MacDonald and P. L. Greenhaff
Department of Physiology and Pharmacology, University Medical School, Queens Medical Center, Nottingham, United Kingdom.
The metabolic effects of partial ischemia on canine skeletal muscle were
examined during 20 min of isometric contraction. A reduction in blood flow
of approximately 75% resulted in an approximate 40% reduction in
contractile function. Muscle lactate accumulation and phosphocreatine (PCr)
hydrolysis were greater during ischemia, indicating a greater reliance on
anaerobic ATP regeneration. Pyruvate dehydrogenase transformation to its
active form (PDCa) during contraction was not affected by ischemia, such
that PDCa did not appear to be a determinant of skeletal muscle fatigue.
Acetylcarnitine concentration was greater during ischemic contraction and
inversely correlated with PCr concentration (r = -0.79, P<0.01).
Furthermore, acetylcarnitine accumulation and PCr degradation correlated
with the degree of skeletal muscle fatigue (r = 0.56, P<0.05 and r =
0.70, P<0.01, respectively). Thus the greater the acetyl group
oxidation, the lesser the contribution from anaerobic ATP provision and,
subsequently, the smaller the degree of muscle fatigue observed. The
metabolic characteristics of this model of ischemic muscle contraction are
indistinguishable from the normal metabolic responses observed with
increasing contractile intensity.
