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Metabolic Inhibitors and Nucleotide Turnover

II. Inhibition of Uptake of C¹⁴-Precursors in Rat Liver and Hepatoma Slices^*

William C. Werkheiser and Donald W. Visser

( Department of Biochemistry and Nutrition, University of Southern California, Los Angeles, Calif.)

The incorporation of formate-C¹⁴ and of carbamyl aspartate-4-C¹⁴ into ribonucleic acid purines and pyrimidines, respectively, of slices of rat liver and of a rat hepatoma have been investigated. The effect on this incorporation of 2,6-diaminopurine and 5-aminouridine, both singly and in combination, has also been studied.

It was found that formate was incorporated specifically into the purines and carbamyl aspartate into the pyrimidines. The degree of labeling of nucleic acid adenine from formate was greater than that of guanine, and in like manner the degree of labeling of uracil from carbamyl aspartate was greater than that of cytosine.

5-Aminouridine caused a profound, uniform inhibition of incorporation into both purines and pyrimidines of liver and a mild, uniform inhibition into those of hepatoma. 2,6-Diaminopurine caused a mild inhibition of incorporation of both precursors into the liver ribonucleic acid and into the pyrimidines of hepatoma and a profound inhibition into the purines of hepatoma.

In addition, both the purine analog and the pyrimidine analog have been shown to inhibit incorporation of formate into purine and carbamyl aspartate into pyrimidine nucleotides.

^* This work was supported by a grant from the California Section of the American Cancer Society. Some of the facilities were made available by the Allan Hancock Foundation.

Present address: Department of Biochemistry, Oxford University, Oxford, England.

Received 11/29/54.