Journal of Applied Physiology, Vol 73, Issue 2 510-515, Copyright © 1992 by American Physiological Society
Hepatic adaptations to iron deficiency and exercise training
W. T. Willis, P. H. Jones, R. Chengson and P. R. Dallman
Department of Pediatrics, School of Medicine, University of California, San Francisco 94143.
Brooks et al. [Am. J. Physiol. 253 (Endocrinol. Metab. 16): E461-E466,
1987] demonstrated an elevated gluconeogenic rate in resting iron-deficient
rats. Because physical exercise also imposes demand on this hepatic
function, we hypothesized that exercise training superimposed on iron
deficiency would augment the hepatic capacity for amino acid
transamination/deamination and pyruvate carboxylation. Sprague-Dawley rats
(n = 32) were obtained at weaning (21 days of age) and randomly assigned to
iron-sufficient (dietary iron = 60 mg iron/kg diet) or iron-deficient (3 mg
iron/kg) dietary groups. Dietary groups were subdivided into sedentary and
trained subgroups. Treadmill training was 4 wk in duration, 6 days/wk, 1
h/day, 0% grade. Treadmill speed was initially 26.8 m/min and was decreased
to 14.3 m/min over the 4-wk training period. The mild exercise-training
regimen did not affect any measured variable in iron-sufficient rats. In
contrast, in iron-deficient animals, training increased endurance capacity
threefold and reduced blood lactate and the lactate-to-alanine ratio during
submaximal exercise by 34 and 27%, respectively. The mitochondrial
oxidative capacity of gastrocnemius muscle was increased 46% by training.
However, the oxidative capacity of liver was not affected by either iron
deficiency or training. Maximal rates of pyruvate carboxylation and
glutamine metabolism by isolated liver mitochondria were also evaluated.
Iron deficiency and training interacted to increase pyruvate carboxylation
by intact mitochondria. Glutamine metabolism was increased roughly
threefold by iron deficiency alone, and training amplified this effect to a
ninefold increase over iron-sufficient animals.(ABSTRACT TRUNCATED AT 250
WORDS)
