Nuclear enlargement--an early change produced in mouse epidermis by carcinogenic chemicals applied topically in the presence of a promoter.

A series of 27 compounds, including 11 polycyclic hydrocarbons, 8 proximate carcinogens and 8 other compounds, were tested for their ability to induce epidermal nuclear enlargement in mouse skin. The materials were applied topically in methyl ethyl ketone containing 0.1% croton oil, repetitively for 3 days. Nuclear enlargement present on the fourth day was determined with the aid of a Quantiment image-analysing computer. The results obtained indicated a close correlation between the topical carcinogenicity of the test compounds and their ability to induce epidermal nuclear enlargement in the presence of croton oil.