Effect of iron loading on non-heme iron compounds in different liver cell populations.

Concentrations of total non-heme iron and ferritin iron were determined for whole livers and isolated Kupffer cells of rats before and after iron treatment. Rats were injected either once, with iron dextran (25 mg of iron), or multiple times, with hemoglobin (totaling 16 mg of iron) or iron dextran (totaling 140 mg of iron), 1 or 16 to 20 weeks before use. Particularly at the highest iron dosage, the liver contained a large proportion of the dose administered as non-heme iron, and, in control rats or rats treated with 16 to 25 mg of iron, 70 to 80% of this iron was in the form of ferritin. A nonhepatocyte fraction, containing mostly Kupffer cells, was isolated from each liver after differential digestion of the hepatocytes by Pronase. In all cases, very little ferritin could be shown in the Kupffer cell fraction by antibody precipitation or disc’ electrophoresis following extraction of the cells with heat treatment, sonic oscillation, and detergents, in various combinations. The Kupffer cell fraction did, however, contain at least two other forms of non-heme iron visualizable by electrophoresis as a very slow migrating band and as large brown granules which did not enter the gel. These granules were isolated in the case of the rats treated with 140 mg of iron and had an iron-protein ratio of 1.9. Based on known values for the percentage of nonhepatocyte nuclei in liver, the total contents of non-heme and ferritin iron in hepatocytes and nonhepatocytes were calculated. The hepatocytes invariably contained almost all of the ferritin iron while the Kupffer cell fraction contained almost all of the nonferritin, non-heme iron. The protein content of the Kupffer cell fraction was commensurate with its estimated contribution to liver volume.