This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Blocker, R. Articles by Roth, J. S. Search for Related Content PubMed PubMed Citation Articles by Blocker, R. Articles by Roth, J. S.

The Reduction of Uridine 5'-Diphosphate and Uridine 5'-Triphosphate in Some Transplantable Rat Hepatomas¹

Section of Biochemistry and Biophysics, Biological Sciences Group, The University of Connecticut, Storrs, Connecticut 06268

The reduction of uridine 5'-diphosphate (UDP) and uridine 5'-triphosphate (UTP) has been studied in normal adult rat liver, the Dunning hepatoma, and Morris 5123D and 7793 hepatomas. A new paper chromatographic method that separates and quantitates all the major products of the reduction and hydrolysis or other reactions of the substrate has been devised. All of the above tissues were able to reduce UDP and UTP at relatively slow rates ranging from 0.25 nmole of deoxycompound formed (deoxyuridine 5'-triphosphate) per mg protein per hr for liver to 3.5 nmoles deoxyuridine 5'-triphosphate for the Morris 7793 hepatoma when UTP was the substrate. In general, UTP was a better substrate than UDP. The method may also be used to measure cytidine 5'-diphosphate (CDP) reduction, and under the same conditions, the reduction of CDP proceeded at about 6 times the rate of UTP reduction in the Dunning hepatoma.

Like CDP reduction, the reduction of UTP was strongly modulated by ATP. Reduction of UTP was insignificant with no ATP or 1.5 µmoles ATP added to the reaction mixture and was maximal with 0.25 µmole.

The reduction of UTP was inhibited by deoxyuridine 5'-monophosphate, deoxythymidine 5'-triphosphate, deoxycytidine 5'-triphosphate, and deoxyribose 1'-phosphate.

The effects of deoxyadenosine 5'-triphosphate varied, depending on its concentration in the reaction medium and whether UDP or UTP was a substrate. However, hydroxyurea did not inhibit reduction of UDP or UTP at concentrations that strongly inhibited CDP reduction.

All of the tissues were able to hydrolyze [-³²P]deoxyuridine 5'-triphosphate readily to the diphosphate and monophosphate.

It is suggested that the enzyme that reduces UTP or UDP may be different in these tissues from the enzyme that reduces CDP.

¹ This research was supported by grants from the Damon Runyon Memorial Cancer Fund, National Cancer Institute Grant CA 08384, and American Cancer Society Grant P-303.

² Recipient of Career Award RC 31–63 from the National Cancer Institute, NIH.

Received 7/28/76. Accepted 2/16/77.