Fluorescent Concentrates from the Nonsaponifiable Fractions of Human Livers*

The laboratory preparation of 20-methylcholanthrene from desoxycholic acid by Wieland and Dane (20) in 1933 encouraged speculation concerning the role that polynuclear aromatic hydrocarbons might play as endogenous carcinogenic agents, but in the succeeding decade progress in the characterization of endogenous chemical carcinogens has been extremely slow. Several investigators have attempted to demonstrate the existence of such agents, and the positive results described by des Ligneris (2); Hieger (4); Sanni~ and his co-workers (13, 14); Kleinenberg, Neufach, and Schabad (8, 9); and Steiner (17-19) suggest that chemical carcinogens may indeed be present in the fatsoluble extracts of certain human livers. Should the presence of chemical carcinogenic agents in a specific tissue be established positively the isolation of the carcinogen would become of pressing interest, but progress in such work would be extremely slow if, at each stage of the fractionation, the potency of concentrates had to await assay by animal experimentation. One cannot, of course, assume that a carcinogen must be a polynuclear aromatic hydrocarbon merely on the grounds that it occurs in the nonsaponifiable fractions of liver extracts. The fact remains, however, that if such hydrocarbons are present in liver one would expect to find them in this fraction. It seemed to us worth while to try to develop fractionation technics suitable for the separation of polynuclear aromatic hydrocarbons from the commoner constituents of nonsaponifiable material. Polynuclear aromatic hydrocarbons, both carcinogenic and noncarcinogenic, usually exhibit blue fluorescence and, at sufficiently high concentrations, give characteristic ultraviolet absorption spectra. Sanni~, Truhaut, Gu&in, and Gu&in (13) examined the ultraviolet absorption spectra of the nonsaponifiable fractions of human liver, and reported no evidence of structure suggestive of the presence of benzpyrene