Location of Absorbed Carcinogens within the Amphibian Cell

Abstract

Cells from explants of newt gastrulae which had been cultured in Holtfreter's standard solution containing the carcinogen 3:4-benzpyrene rendered soluble by caffeine were examined for fluorescence by ultra-violet light. The lipoid constituents of the cells, lipochondria and liposomes, showed the bright blue fluorescence of benzpyrene in molecular solution and there was also occasionally a structureless blue fluorescence round the nucleus corresponding, perhaps to the so-called ‘Golgi Apparatus’. The yolk platelets were slightly fluorescent but this was probably due to the associated lipides and it largely disappeared in moribund preparations, where the lipochondria became detached from the platelets. The nucleus showed no fluorescence, nor was a, fluorescent nucleolus observed. It could be shown that the pyronine staining cytoplasmic granules of ribonucleoprotein (microsomes) were not fluorescent and so probably do not have any affinity for the carcinogen. The very small fluorescent granules in Brownian movement that had previously been looked upon as ribonucleoprotein microsomes are in fact small liposomes and do not stain with pyronine. It is suggested that the evocating power of the carcinogenic hydrocarbons is probably not due to cytolytic activation of the evocator, by the killing of some cells in the exposed ectoderm. It may be by physiological activation, operating through a specific action on the lipochondria, leading to their breakdown into liposomes and the release of active evocator substance. Some evidence is produced which suggests that the lipochondria contain ribonucleoprotein, and this fraction of them may constitute the active evocator; this would be congruent with the theories of Brachet (1947). It cannot yet be excluded, however, that the hydrocarbons act as direct evocators, simulating the effects of the naturally occurring substance. The observation that benzpyrene is not accumulated by nucleoprotein makes it likely that the mutagenic activity of the carcinogens is indirect.