A quantitative determination of the covalent binding of a series of polycylic hydrocarbons to dna in mouse skin

The extents of reaction of seven 3 H‐labelled polycyclic hydrocarbons with DNA in mouse skin following their topical application have been studied. DNA isolated from the treated areas was hydrolysed enzymically to deoxyribonucleosides and the products chromatographed on Sephadex LH20 columns. The levels of binding of hydrocarbon to DNA were determined from the amounts of radioactivity eluted from Sephadex LH20 columns in those fractions containing hydrocarbon‐DNA adducts. Tritium incorporation into normal deoxyribonucleosides was examined by rechromatography of material on AG50W‐X4 columns and in some instances was found to account for a substantial proportion of the total radioactivity associated with DNA samples. Following treatment of mice with 1 (imol hydrocarbon/mouse, 7, 12‐dimethylbenz( a )anthracene, the most potent carcinogen studied, became bound to DNA to the greatest extent (43 pmol/mg DNA), Benzo( a )pyrene and 3‐methylcholanthrene, the next most active compounds, became bound to DNA to similar extents (27 pmol/mg DNA and 25 pmol/mg DNA), as did 7‐methylbenz( a )anthracene (25 pmol/mg DNA) although it is a less active compound. Dibenz‐( a , h ) anthracene, another moderately active hydrocarbon, became bound to DNA to the extent of 15 pmol/mg DNA, and the very weakly active compounds, benz( a )anthracene (2 pmol/mg DNA) and dibenz( a , c ) anthracene (10 pmol/mg DNA) became bound to DNA to the lowest extents. Dibenz( a , h ))anthracene differed from the other hydrocarbons in showing a maximum level of binding 72 h after treatment, compared with 19–24 h for the other compounds.