Influence of iron-saturation of plasma transferrin in iron distribution in the brain

Abstract

Based on the evidence that iron distribution in the peripheral tissues is changed by iron-saturation of plasma transferrin, the influence of iron-saturation of plasma transferrin in iron delivery to the brain was examined. Mouse plasma was pre-incubated with ferric chloride in citrate buffer to saturate transferrin and then incubated with 59FeCl 3. Peak retention time of 59Fe was transferred from the retention time of transferrin to that of mercaptalbumin, suggesting that iron may bind to albumin in the plasma in the case of iron-saturation of transferrin. When mice were intravenously injected with ferric chloride in citrate buffer 10 min before intravenous injection of 59FeCl 3, 59Fe concentration in the plasma was remarkably low. 59Fe concentration in the liver of iron-loaded mice was four times higher than in control, while 59Fe concentration in the brain of iron-loaded mice was approximately 40% of that of control mice. Twenty-four hours after intravenous injection of 59FeCl 3, brain autoradiograms also showed that 59Fe concentrations in the brain of iron-loaded mice were approximately 40–50% of those of control mice in all brain regions tested except the choroid plexus, in which 59Fe concentration was equal. These results suggest that the fraction of non-transferrin-bound iron is engulfed by the liver, resulting in the reduction of iron available for iron delivery to the brain in iron-loaded mice. Transferrin-bound iron may be responsible for the fraction of iron in circulation that enters the brain.