Chromosome aberrations induced by 7,12-dimethylbenz[a]-anthracene in bone marrow cells of spontaneously hypertensive rats (SHR) and control Wistar Kyoto (WKY) rats: time course and site specificity.

The frequency of chromosome aberrations (CA) induced by iv injection of 7,12-dimethylbenz[a]anthracene [(DMBA) CAS: 57-97-6] was examined with the use of control Wistar Kyoto (WKY) rats and spontaneously hypertensive rats (SHR). SHR appear to be analogous to hypertensive humans, since evidence has been reported of a difference in tumor susceptibility between SHR and WKY strains. Injection of DMBA evoked CA in bone marrow cells of both SHR and WKY rats. The frequency of CA in SHR was significantly higher than in WKY rats at 12 and 18 hours after DMBA treatment. With regard to the relative frequencies of aberrations in SHR and WKY rats, chromosomes 1 and 2 were more susceptible to DMBA-induced CA. The proportion of breaks that occur in the "hot spot" at 6 hours after DMBA treatment was distributed nonrandomly at a site approximately 40% of the total length from the centromere in chromosome 1 and at lengths of approximately 30 and 55% in chromosome 2. The specific distribution of CA seemed to be caused by a cell cycle-specific effect. These results, confirming nonrandom CA induced by DMBA in bone marrow cells of WKY rats, are similar to previous reports in which Long-Evans rats were used. Thus they indicate that a common mode of action by DMBA at the chromosome level in rat bone marrow cells was observed in different strains and that SHR were more sensitive than WKY rats to CA induced by DMBA.