Sodium fluorescein accumulation in cultured cells.

The mechanism of intracellular fluorescein accumulation was investigated by studying fluorescein accumulation kinetics in individual cells in culture. The experiments were done with K562 human erythroleukemia cell culture and a primary culture of human embryonic skin fibroblasts. Various experimental conditions were used by varying pH and ion composition of the external media, and/or temperature. All the experimental results obtained are in support of the proposed theoretical model describing fluorescein accumulation in cells along the pH gradient. In addition, we could show that fluorescein molecules are bound to some intracellular macromolecules. Fluorescein accumulation in the cells studied does not depend on their malignant nature. It is therefore reasonable to conclude that fluorescein accumulation observed in clinical investigations of human gastric cancer is governed by the ph gradient between the cells and the extracellular fluid; this gradient is much greater in the tumor than in normal tissues.