EFFECTS OF AROMATIC ISOTHIOCYANATES ON TUMORIGENICITY, O-6-METHYLGUANINE FORMATION, AND METABOLISM OF THE TOBACCO-SPECIFIC NITROSAMINE 4-(METHYLNITROSAMINO)-1-(3-PYRIDYL)-1-BUTANONE IN A/J MOUSE LUNG

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  • 1 June 1989
    • journal article
    • research article
    • Vol. 49  (11) , 2894-2897
Abstract
Phenethylisothiocyanate (PEITC), benzylisothiocyanate (BITC), and phenylisothiocyanate (PITC) were tested for their abilities to inhibit lung tumorigenesis and O6-methylguanine formation in lung DNA induced by the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in A/J mice. Pretreatment with PEITC for 4 consecutive days at daily doses of 5 or 25 .mu.mol inhibited tumor multiplicity induced by a single 10-.mu.mol dose of NNK by approximately 70% or 97%, respectively. The 25-.mu.mol daily dose of PEITC also reduced the percentage of animals that developed tumors by 70%. In contrast, both BITC and PITC failed to significantly reduce tumor multiplicity or the percentages of mice that developed tumors. Using an identical dosing regimen, parallel results were observed in the effects of these isothiocyanates on O6-methylguanine formation in the lung, in which PEITC at either dose resulted in considerable inhibition at 2 or 6 h after NNK administration, while BITC and PITC had little effect. PEITC was further tested for its ability to inhibit lung microsomal metabolism of NNK. A single administration of PEITC (5 or 25 .mu.mol) resulted in 90% inhibition of NNK metabolism. These results in conjunction with recent results obtained using F344 rats firmly establish PEITC as an effective inhibitor of NNK lung tumorigenesis and suggest that the basis of this inhibition is the reduction of DNA adduct formation caused by the inhibition of enzymes responsible for NNK activation.