The Inhibitory Effect of Theophylline on the Incorporation of 3 H-Deoxycytidine and 3 H-Thymidine into Thymocyte DNA

Abstract

Summary

In short term cultures of rat thymic lymphocytes, theophylline caused an early inhibition of incorporation of ³H-de-oxycytidine into DNA without influencing the incorporation of ³H-thymidine. Over a 4-hr incubation period, the inhibitory effect of theophylline on ³Received H-deoxycytidine uptake into DNA remained at approximately 40%, while the suppression of ³H-thymidine uptake increased to 20%. The results indicate that since there is a difference in the effect of theophylline on the incorporation of ³H-deoxy-cytidine and ³H-thymidine into the DNA of thymus lymphocytes, inhibition of uptake of these deoxynucleosides by theophylline does not necessarily reflect inhibition of DNA synthesis or cell turnover.

This investigation was supported in part by PHS Grants No. CA 10291 and T12CA8021-03 from the National Cancer Institute. We are grateful to Mrs. Mary Alyce Vornholt for technical assistance.