The assay of iron-poly (sorbitol-gluconic acid) complex (Ferastral) and its separation from transferrin in serum.

A new iron-poly (sorbitol-gluconic acid) complex (Ferastral) has been studied. A method of assay is described. The iron complex may be separated from serum transferrin using a Sephadex DEAE A50 column. This binds the iron complex and elutes iron-transferrin which can then be assayed. It is shown that the assay of serum transferrin unsaturated binding capacity using excess 59FeCl2 and MgCO3 adsorption, is valid in the presence of Ferastral. Serum unsaturated iron binding capacity may therefore be used to follow the binding of Ferastral iron by transferrin. These methods may be used to follow the distribution of iron in plasma after an intramuscular injection of Ferastral.

Transfer of iron from Ferastral and other organic complexes to transferrin as measured by reticulocyte uptake.

The transfer of iron from the iron carbohydrate complexes, Ferastral, Imferon, and Jectofer, and from ferric chloride has been studied by the effect of such transfer in reducing reticulocyte uptake of 59Fe from labelled transferrin. There are plasma factors which augment the transfer of iron from complex to transferrin. The pattern of transfer from Ferastral and from Imferon are similar: at concentration of 5000 microgram/100 ml and 1250 microgram/100 ml in plasma these complexes transfer about 0.8% and 1.7%, respectively. Jectofer transfers about four times these amounts under similar conditions. In the case of Ferastral there is evidence of an equilibrium between transferrin-bound and Ferastral-bound iron. The characteristics of Ferastral assessed in this way suggest that it may prove suitable for therapeutic use as a total dose infusion.

Patterns of plasma iron fractions after intramuscular Ferastral.

The distribution of plasma iron fractions after intramuscular Ferastral is described for times up to eight days after injection. Transferrin-bound iron reaches a peak value in 4-8 hours and falls towards normal values while circulating iron-complex concentration remains high. The peak concentration of iron-complex occurs 8-24 hours after injection, and is virtually cleared from the circulation in 6-8 days. An approximate T 1/2 of 30 hours for plasma Ferastral is deduced from the rate of fall from peak values. UIBC values fell as transferrin-bound iron increased, but did not reach zero in any subject studied.