Increased nitric oxide is one of the causes of changes of iron metabolism in strenuously exercised rats

This study was carried out to investigate the possible role of increased ni tric oxide (NO) production in the development of the low iron status in str enuously exercised rats. Female Sprague-Dawley rats were randomly assigned to four groups: sedentary (S1), sedentary + nitro-L-arginine methyl ester ( L-NAME; S2), exercise (E1), and exercise + L-NAME (E2). Animals in the E1 a nd E2 groups swam for 2 h/day for 3 mo. L-NAME in the drinking water (1 mg/ ml) was administrated to rats in the S2 and E2 groups for the same period. At the end of third month, hematological indexes and nitrite and nitrate (N Ox) contents in the plasma and non-heme iron and NOx levels in the liver, s pleen, and bone marrow cells were measured. Three months of exercise induce d a significant increase in NOx content and a decrease in iron level both i n plasma and tissues. Treatment with L-NAME, an inhibitor of NO synthase (N OS), led to a significant decrease in NOx and an increase in iron level bot h in plasma and tissues in the exercised rats. The E2 group had a significa ntly lower NOx content as well as a higher iron level both in plasma and ti ssues than the E1 group. However, the iron contents in the plasma and tissu es of the E2 group were still significantly lower than those found in S1. N o difference was found in NOx levels between E2 and S1. These findings show ed that exercise was associated with elevation in NOx and reduction in iron in plasma and the tissues. Treatment with L-NAME was able to completely in hibit the effect of exercise on NOx as well as partly recover the decreased iron contents in plasma and tissues resulting from exercise. This suggests that the increased production of NO might be one of the causes of the lowe r iron status in exercised rats.