The Radiosensitivity of Escherichia coli and Streptococcus faecalis as Influenced by Vitamin K 5 and Its Analogs

Abstract

Six compounds structurally related to and including vitamin K5 were examined for their ability to increase the lethal effects of gamma-radiation on E. coli and S. faecalis. Two compounds, 4-amino-1-naphthol and 1-amino-2-naphthol, increased the lethal effects of ionizing energy to a greater extent than vitamin K5 for both test organisms. All 3 compounds were most effective against E. coli only in the absence of oxygen. In contrast, S. faecalis was influenced both in the presence and in the absence of oxygen, although, in general, to a greater extent in its absence. In addition, menadione sodium bisulfite and 5-amino-1-napthol were active against S. faecalis irradiated in a nitrogen atmosphere. The methyl group in vitamin K5 is responsible for this compound''s being less effective than 4-amino-l-naphthol, and shifting the amino group to the adjacent ring in amino naphthol decreased or eliminated synergism. The implications of whether or not these compounds are exerting true enhancing or sensitizing mechanisms or a combination of these effects are discussed.