Membrane transport properties of L-2,4-diaminobutyrate revisited

We explore here the special structural features of certain diamino acid analogs which may account for their intense accumulation into tumor cells, first observed for the Ehrlich ascites tumor cell for in vitro suspensions. This accumulation, which ordinarily occurs mainly by system A for its dipolar substrates, is so intense for these tripolar diamino acids accompanied by the chloride ion as well as by displacement, especially of the cellular potassium ion, that the cells swell to several times their normal volume and osmotic destruction arises. These structural features receive our reconsideration here toward understanding the energization of amino acid transport into cells, also toward identifying among them possible superior 11C-labeled tracers for imaging tumors in situ by positron emission tomography (PET). The possibility of therapeutic, perhaps osmotic, destruction of inoperable terminal gliomas by topical application of such amino acids by microdialysis has also been considered in preliminary tests by one of us (G.R.) and his associates.