The microheterogeneity of human liver and serum ferritins measured on minute amounts of ferritin in crude samples.

A method is presented to measure the microheterogeneity of ferritin in micrograms amounts, without purifying the samples extensively. Ferritin-containing samples such as serum and homogenized liver-biopsy specimens were mixed with Sephadex G-75 and ampholines. Isoelectric focussing was performed and the pH gradient in the Sephadex was measured. The Sephadex was divided into predetermined pH ranges and the ferritin eluted from these fractions. Ferritin concentration was measured by an enzyme-linked immunosorbent assay. The method proved to be reproducible. The isoferritin profiles of different human serum and liver tissue samples were quite variable. In most cases serum ferritins focussed between approximately pH 5.5 and pH 4.9 and liver ferritins between approximately pH 5.8 and pH 5.3. We examined whether there was a similarity in the isoferritin patterns of serum and liver of distinct patients. We also studied liver tissue and serum from a patient with haemochromatosis and from a child with iron overload of unknown origin. In the serum of our patients the isoferritin pattern had shifted to lower pI when compared with that found in liver tissue. Only in the case of a patient with transfusion iron overload were basic isoferritins measured in the serum. In this case no liver biopsy specimen was available for comparison.