[Mutagenicity of organic rubber additives].

The DNA-damaging activities of organic rubber additives such as rubber vulcanizing agents, vulcanization accelerators and rubber anti-oxidants were investigated by the rec-assay using spores of Bacillus subtilis strains H 17 and M 45. For metabolic activation, 9,000 X g supernatant solutions of the liver homogenate of Sprague-Dawley male rats previously treated with aroclor 1,254 were used. Spore rec-assays were carried out at the dose of 1 mg/disk, and the ratio of inhibition zones for M 45 to that for H 17 was calculated. Samples showing a ratio of more than 1.2 were judged positive. In order to know the DNA-damaging capacity of positive samples, the dose-response curves were prepared by carrying out the assays at various doses, and minimal inhibition concentration (MIC) for H 17 and M 45 was obtained from these curves by extrapolation. Then indices of DNA damagenicity were calculated through division of the MIC obtained with H 17 by that with M 45. The 0.005 micrograms/disk of mitomycin C and at 4 micrograms/disk of Trp-P1 were used as positive control, and the 50 micrograms/disk of kanamycin as negative control. The results obtained are as follows: Among 20 tested samples, p-quinone dioxime, bis-morpholine disulfide used as rubber vulcanizing agents and hexamethylenetetramine, zinc butylxanthate used as vulcanization accelerators gave positive results. It was considered that the action of hexamethylenetetramine against DNA was due to the electrophilic state of this material. Furthermore, we supposed that DNA-damaging activity of p-quinone dioxime was concerned with free hydroxyl groups of this compound.(ABSTRACT TRUNCATED AT 250 WORDS)