P-32 POST-LABELING ANALYSIS OF DNA ADDUCTS FORMED IN THE LIVERS OF ANIMALS TREATED WITH SAFROLE, ESTRAGOLE AND OTHER NATURALLY-OCCURRING ALKENYLBENZENES .1. ADULT FEMALE CD-1 MICE

The binding of a series of alkenylbenzenes to liver DNA of adult female CD-1 mice, isolated 24 h after i.p. administration of non-radioactive test compound (2 or 10 mg/mouse), was investigated by a modified 32P-post-labeling assay. The known hepatocarcinogens safrole, estragole and methyleugenol exhibited the strongest binding to mouse liver DNA (1 adduct in 10,000-15,000 DNA nucleotides or 200-300 pmol adduct/mg DNA after administration of a 10 mg dose); several related compounds, which have not been shown thus far to be carcinogenic in rodent bioassays, bound to mouse liver DNA at 3-200x lower levels. The latter compounds included allylbenzene, anethole, myristicin, parsley apiol, dill apiol and elemicin. Eugenol did not bind. Low binding to mouse liver DNA was also observed for the weak hepatocarcinogen isosafrole. Two main 32P-labeled adducts, which appeared to be guanine derivatives, were detected for each of the binding chemicals on TLC. The loss of safrole adducts from liver DNA was biphasic: a rapid loss during the 1st wk (t1/2 [half-life] .apprx. 3 days) was followed by a much slower decline up to 20 wk after treatment (t1/2 .apprx. 2.5 mo.). Adducts formed by reaction of 1''-acetoxysafrole, a model ultimate carcinogen, with mouse liver DNA in vitro were chromatographically identical to safrole-DNA adducts formed in vivo. Pretreatment with pentachlorophenol, a known inhibitor of sulfotransferases, inhibited the binding of safrole to mouse liver DNA, providing further evidence that the metabolic activation of the allylbenzenes proceeds by the formation of 1''-hydroxy derivatives as proximate carcinogens and 1''-sulfoxy derivatives as ultimate carcinogens.