Nitric oxide production and inducible nitric oxide synthase induction in iron-loaded rats

We investigated effects of iron on iNOS induction and NO production in vivo. We prepared chronic iron-loaded rats with diets supplemented with carbonyl iron and induced NO in vivo by an i.p. injection of lipopolysaccharide (LPS, 5.0 mg/kg body wt.). On immunohistochemical study, iNOS was induced in hepatic Kupffer cells, splenic and lung alveolar macrophages, monocytoid cells in pulmonary vessels at 6 hours after LPS injection in iron-loaded and control rats in the same manner, but in iron-loaded rats many Kupffer cells showed both iNOS and iron deposition. On western blotting, iNOS was induced in liver, spleen and lung at 6 hours after LPS injection and iNOS induction was more enhanced in iron-loaded liver than the control. To assess NO production, nitrosyl hemoglobin (NO-Hb) in blood was measured by EPR, and nitrite and nitrate (NOx) in serum by Griess method. NO-Hb and NOx increased rapidly after LPS injection and showed a peak at 6 hours and decreased until 48 hours. NO-Hb and NOx productions were not significantly different between iron-loaded and control rats. Chronic iron-loading enhanced iNOS induction in the hepatic Kupffer cells compared with the control, but did not change NO concentration of blood because the concentration means total NO production not only from the Kupffer cells, but also from the other all organs.