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Changes in Polyamine Levels and Protein Synthesis Rate during Rat Liver Carcinogenesis Induced by 4-Dimethylaminoazobenzene¹

Institute of General Pathology [A. P.] and Consiglio Nazionale delle Ricerche Center for Research in Cell Pathology [A. S.], University of Milan, Via Mangiagalli, 31, 20133 Milan, Italy

The concentrations of putrescine, spermidine, and spermine in liver of rats fed on 4-dimethylaminoazobenzene and in the resultant hepatomas were found to be significantly higher than were those observed in normal liver from rats of the same strain, sex, and age. These modifications were due to the carcinogen and not to the special low-riboflavin diet used to obtain the carcinogenic effect of 4-dimethylaminoazobenzene. The first change observed during liver carcinogenesis was the early increase in the putrescine level, followed by an increase of spermidine and spermine, which reached maximum levels in growing hepatomas. A significant increase of urinary polyamines was also observed in tumor-bearing rats. Experiments on leucine incorporation into proteins of tissue slices, which were obtained from the same tissues on which polyamine determinations were carried out, showed that in rat liver carcinogenesis the rate of protein synthesis was well correlated with the polyamine levels. These results suggest that polyamines may play a role in the process of carcinogenesis and in tumor protein synthesis in vivo.

¹ This study was supported by the Consiglio Nazionale delle Ricerche, Rome, Italy.

² To whom requests for reprints should be addressed.

Received 6/13/77. Accepted 9/22/77.