Concentration of gallium-67 by V79 multicellular spheroids

Abstract The concentration of gallium-67 by the V79 cell line was studied in the multicellular spheroid tumor model in tissue culture. The spheroids display histologic features and growth characteristics similar to those of a rapidly growing tumor that is outgrowing its blood supply. Maximum gallium concentration occurred in the spheroids in the presence of fresh growth medium but an energy requirement for gallium uptake could not be demonstrated. We concluded that the metabolites present in exhausted medium interfere with gallium uptake. During hypoxia the uptake was increased. Autoradiography showed that most of the gallium concentrated in hypoxic central zones of the spheroids. Dead spheroids had a markedly increased affinity for gallium and the preference for the central zones was eliminated. In these cells and under these conditions of culture gallium uptake is apparently related to permeability of cell membranes alone. Alterations in the cellular environment which may result in membrane injury increase the uptake. Hypoxic zones in rapidly growing tumors may be sites of preferred gallium uptake by mechanisms that are not related to transferrin-mediated gallium transport.