Changes in tRNA methylase activity of rat kidney following administration of the carcinogen, dimethylnitrosamine

1. 1. Administration of dimethylnitrosamine (40 mg/kg body wt) to rats being fed a diet deficient in protein led to an increase in the tRNA methylase activity of the kidney. Maximum activity occurred 2 days after the dimethylnitrosamine was given and a second peak of activity occurred about 4 days later after which the activity declined to normal values. 2. 2. Kidney tumours are produced in a high yield as a result of this treatment and the tumours which appeared some months later also had a higher tRNA methylase activity than control normal kidney. The enhanced tRNA methylase activity appeared to be a general response of all the enzymes detectable by assay with the tRNAs from yeast and Escherichia coli used as substrates. 3. 3. These results are discussed in terms of the changes in nucleic acid synthesis produced in the kidney by dimethylnitrosamine and studies of the histological development of kidney tumours.