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Deoxycytidine Kinase and Cytosine Nucleoside Deaminase Activities in Synchronized Cultures of Normal Rat Kidney Cells¹

Ontario Cancer Institute and Department of Medical Biophysics, University of Toronto, 500 Sherbourne Street, Toronto, Ontario, Canada M4X 1K9

Previous work has suggested that 1-ß-D-arabinofuranosylcytosine 5'-triphosphate is the active metabolite of 1-ß-D-arabinofuranosylcytosine. The amount of 1-ß-D-arabinofuranosylcytosine 5'-triphosphate formed in tissues has been shown to be influenced by the relative levels of deoxycytidine kinase and cytosine deaminase. In this study we have measured the intracellular levels of deoxycytidine kinase and cytosine deaminase activities in synchronized cultures of normal rat kidney cells. The deoxycytidine kinase activity was found to be cell cycle related with a minor peak of activity in early G₁ phase and a major peak of activity in middle and late S phase. The cytosine deaminase activity was also found to be cycle dependent with a peak of activity at G₁ phase and another at S phase of the cell cycle. Similar results were obtained when cytosine deaminase activities were measured with cytidine, deoxycytidine, or 1-ß-D-arabinofuranosylcytosine as substrate. Present studies also confirmed earlier studies by other workers that the main effect of 1-ß-D-arabinofuranosylcytosine is in the late S phase of the cell cycle.

¹ This work is supported by a grant from the Medical Research Council of Canada.

² Recipient of a studentship from the National Cancer Institute of Canada.

Received 11/29/77. Accepted 6/ 5/78.

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