Effect of o,p'-DDD on the in Vivo Incorporation of 3H-Thymidine into DNA: Evidence for Induced Cell Proliferation in the Mouse Lung.

The effects of o,p'-DDD on the DNA synthesis in the C57B1 mouse lung and liver were studied. As determined by ³H-thymidine incorporation into DNA, a selective increase in the lung DNA synthesis (+59%) was observed 2 days after a single intraperitoneal injection of 100 mg/kg o,p'-DDD. Microautoradiography showed that the incorporated ³H-thymidine was confined to a restricted number of heavily labelled cells, presumably proliferating type II cells. At the most, a 9 times higher rate of cell proliferation was observed in the lung 4 days after an intraperitoneal injection of 500 mg/kg o,p'-DDD. Using mouse lung or liver S-9 as activating system, no mutagenic activity of o,p'-DDD was detected in the Ames test. The induced cell proliferation may indicate a tissue-selective promotor activity of o,p'-DDD in the mouse lung. [ABSTRACT FROM AUTHOR]