Dependence of 1,2-dimethylhydrazine metabolism on its treatment schedule.

The content of cytochromes P-450 and b5 in rat liver microsomes, as well as the extent of labeling of nucleic acids and proteins of the liver and kidneys and of mucosa from different intestinal segments, was studied in rats injected daily or once a week subcutaneously with similar total doses of 1,2-dimethyl-hydrazine (SDMH) and in untreated rats. Daily SDMH administrations led to a decrease in cytochrome P-450 activity. Pretreatment of rats with unlabelled SDMH resulted in decreased labeling of DNA, RNA, proteins, and acid-soluble fractions after [3H]SDMH injection. A more pronounced effect was found after the daily treatment.