The Physiological Significance of Circulating Transferrin Receptors

Abstract

The safe and efficient transport of iron to body tissues from the gastrointestinal tract and storage organs is accomplished by its binding to transferrin, a specialized glycoprotein with a molecular mass of 80,000 D. The structure and iron-binding properties of this transport protein are well known (Aldred et al., 1987; Worwood, 1989; Thorstensen and Romslo, 1990). In the presence of bicarbonate, transferrin binds two atoms of iron when fully saturated and thereby prevents its precipitation as ferric iron which otherwise occurs at physiological pH. Approximately one-third of circulating transferrin is saturated with iron in normal subjects, tissue iron supply being adequate when the saturation is above 20% (Bothwell et al., 1979).