The Mobilization of Iron from the Perfused Mammalian Liver by a Serum Copper Enzyme, Ferroxidase I

Abstract

Abstract The effect of ferroxidase I (ceruloplasmin) on the mobilization of iron into a buffered solution without plasma proteins in perfused dog and pig livers and the appearance of iron was detected by Fe(III)-transferrin formation and an independent iron analysis. Among the various compounds tested, only ferroxidase I, as low as 4 nm, was capable of mobilizing iron into the perfusate. CuSO4, HCO3- citrate, apotransferrin, glucose, fructose, and serum albumin (±Cu(II)) were inactive. Above 0.2 µm ferroxidase I, the rate of iron mobilization did not increase, suggesting that the efflux of iron from the liver depends not only on ferroxidase activity but also on the rate of labile iron formation and its subsequent diffusion from the iron storage cell. The rate at which iron appears in the perfusate is a function of the ferroxidase concentration. However, the amount of iron mobilized is not dependent on either the ferroxidase or apotransferrin concentration. It is proposed that ferroxidase activity results in the substantial elimination of Fe(II), generating a maximum concentration gradient from the iron stores to the capillary system, thus promoting a rapid iron efflux from the iron storage cells of the perfused liver.