[Cell kinetic effects of crude coal tar application plus long wave ultraviolet radiation on normal and hyperproliferative epidermis of guinea pig skin].

This study investigated the cell kinetic effects of combined treatment with crude coal tar and long wave ultraviolet (UVA) radiation on the normal and n-hexadecane-induced hyperproliferative epidermis of guinea pig skin. Flow cytometry was used to determine the proportion of cells in S phase (S fraction) and G2 + M phase (G2 + M fraction). Bromodeoxyuridine incorporation was used to determine the labeling index. Conventional histologic techniques were used to observe the mitotic index. In the normal epidermis after a single treatment with tar and UVA (1 J/cm2) or tar alone, the labeling index showed an initial decrease of 4 hr duration followed by moderate increase. The initial decrease was more pronounced in the tar-UVA-treated epidermis than in the tar-treated epidermis. The mitotic index was depressed during the first 12 hr. S- and G2 + M fraction showed no changes during the first 12 to 18 hour, and then increased in varying degrees. In the hyperproliferative epidermis after two applications of tar and UVA (1 and 4J/cm2) or tar alone, the labeling index was depressed during the first 12 hr, and mitotic index was below the control level until the 36 hr. The inhibitory effects on DNA synthesis and mitosis were more pronounced in the tar-UVA-treated epidermis than in the tar-treated epidermis. The S- and G2 + M fraction exceeded the control level in varying degrees during the whole experimental period. The results indicate that tar inhibits the epidermal DNA synthesis and mitosis by itself, and that the inhibitory effects of tar are intensified by the radiation of UVA.