Effects of exercise on iron metabolism in rats

The effect of exercise on the uptake, redistribution, and excretion of iron was studied in normal iron-sufficient rats. Rats were run to exhaustion in a “sprint” protocol seven times over a twentyone day period. Exercised rats did not differ significantly from sedentary rats in hemoglobin concentrations or in body or organ weights. Exercised rats absorbed more iron than sedentary rats in radioiron tracer studies. Radioiron accumulated mainly in heart, liver, and spleen. Strikingly, tracer iron accumulated significantly in hearts of exercised rats. Exercised rats had less total iron in liver and spleen than sedentary rats. Myoglobin concentrations in heart and soleus muscles were significantly higher in rats after the exercise regimen and decreased following fourteen days of rest. Brief, strenuous exercise appears to signal increased absorption of iron and to stimulate the redistribution of storage iron. This mobilization of iron during exercise may be directed towards the enhancement of oxygen-accepting ability in muscles at work.