Ploidy patterns in hepatic tumors induced by Mirex.

The effects of chronic exposure to dietary Mirex was investigated in rat livers over a 13 month period. The distribution of ploidy (diploid and tetraploid nuclei) in nodular and nonnodular areas was analyzed in a Coulter Counter fitted with a Channelizer. The nodules, such as adenomas and carcinomas, were identified in histologic sections obtained from companion samples, part of which was used for analysis of nuclear ploidy. The carcinogen disturbed the distribution of nuclei in the ploidy classes, selectively reducing the number of tetraploid cells. This reduction in tetraploid cells corresponded to the nature of the tumor, the most significant effect being noted in hepatocellular carcinomas.