Journal of Applied Physiology, Vol 61, Issue 4 1275-1278, Copyright © 1986 by American Physiological Society
Carnitine metabolism during prolonged exercise and recovery in humans
J. I. Carlin, W. G. Reddan, M. Sanjak and R. Hodach
Lennon et al. (J. Appl. Physiol. 55: 489-495, 1983) have recently reported
a large loss of muscle total carnitine (TC) after 40 min of moderate
exercise. These authors have also suggested that elevations in plasma
esterified carnitine (EC) were due to the release of these carnitine esters
from muscle during exercise. After 10 male subjects underwent 90 min of
cycle egometry we found no alteration in muscle TC from preexercise values.
Plasma EC progressively increased above resting values during exercise and
remained elevated above rest at 0.75 and 1.5 h into recovery. Elevations of
plasma EC were largely due to a decrement in free carnitine (FC) in both
conditions. Immediately postexercise the urinary fractional reabsorbsion of
EC and FC were similar to that at rest. These results suggest that a net
loss of TC from exercising muscle does not occur. As in other conditions
marked by falling insulin concentrations, elevations in plasma EC could
result from an exchange of carnitine with the hepatic carnitine pool.
