Iron deposition in tissues.

Among clinical conditions w ith increased tissue iron, id iopathic hem o­ chrom atosis is un ique. I t is associated w ith increased absorption and iron deposition in all tissues. E xperim ental m odels to study iron absorption and deposition in tissues m ay p rovide inform ation on the processes associated w ith excess iron uptake. Low pro tein high fat d iets induced excess iron deposition in liver of rats. W hen diets contained a balanced am ount of fat, 15 to 18 p ercen t o f p ro te in was necessary for an adequate iron uptake. P art of this p ro tein effect could be explained on the am ino acid facilitated iron absorption from the gastro intestinal tract. Both excess and deficiency of m eth ionine induced iron deposition in liver. In m eth ion ine excess, there was also iron deposition in sp leen associated w ith hem olytic anem ia. In ­ creased am ounts of iron in liver w ere induced also by hom ocystine and excess cystine and in renal tubu les by excess d ietary serine. U sing eth ion ine feed ing as an experim ental m odel, it was estab lished th a t increased liver iron deposition was associated w ith an increased tissue affinity for iron. Such increased affinity for iron may be associated w ith id iopathic hem o­ chrom atosis also. W hile in id iopathic hem ochrom atosis the tissue siderosis is irreversib le, the dietary liver siderosis, induced by corn grits, was re ­ versed after feeding a balanced diet. L iver siderosis and affinity for iron in eth ion ine-fed rats d isappeared on pro longed e th ion ine feeding. A lthough eth ion ine induced inh ib ition of p ro tein synthesis in general, ferritin syn the­ sis was increased. T hus the tissue affinity for iron may be a reflection o f an increased ferritin synthesis. It was suggested th a t ferritin synthesis is in ­ duced by iron at the level o f translation. T he genetic defect in id iopathic hem ochrom atosis may b e associated w ith cell m em brane perm itting in ­ creased transfer of iron. C linical C onditions w ith Increased T issue Iron Excess iron accum ulates as a resu lt of abundan t d ietary con ten t of iron, m ultip le * This report was supported in part by NCI Grant # 3 R26 CA20128-03 through the National Pancreatic Cancer Project. blood transfusions, hem oly tic anem ias, infectious and liver diseases including al­ cohol. In th ese conditions, th e re is no generalized iron deposition in all tissues. It is localized in the liver and sp leen as ferritin and hem osiderin . In id iopath ic hem ochrom atosis, iron is deposited in excessive am ounts in all tis­