Fluorescence measurements of the labile iron pool of sickle erythrocytes

Abstract

Sickle erythrocytes have increased ferritin and increased molecular iron on the inner membrane leaflet, and we postulated that cytosolic labile iron is also elevated. We used the fluorescent metallosensor, calcein, and a permeant Fe2+ chelator to estimate labile cytoslic Fe2+, and calcein plus an Fe3+ chelator to estimate total cytosolic labile iron (Fe2+ + Fe3+). We measured membrane nonheme iron by its reactivity with ferrozine. As estimated by calcein and Fe2+ chelator, the mean ± SD labile Fe2+ concentration was significantly lower in hemoglobin (Hb) SS (n = 29) than hemoglobin AA (n = 17) erythrocytes (0.56 ± 0.35 μM versus 1.25 ± 0.65 μM; P