THYMIDINE TRIPHOSPHATE CONTENT OF REGENERATING RAT LIVER

The endogenous thymidine triphosphate pool has been examined in regenerating rat liver under conditions designed to minimize the breakdown of this substance which is biologically unstable. Thin-layer chromatographic techniques are described that are reliable for small samples (4-5g) of regenerating liver, but inadequate for the low dTTP levels of normal liver. 1. 1. The labeling of thymidine phosphates following a single intravenous injection of [14C]thymidine is initially highest in the monophosphate, but comes to equilibrium after several minutes with approximately 25-30% of the radioactivity in the monophosphate, 10% in the diphosphate and 60-65% in the triphosphate form. 2. 2. The rate of thymidine phosphorylation remains normal for approximately the first half day after partial hepatectomy, then rises steeply, approximately coinciding with DNA replication. 3. 3. The endogenous dTTP pool is 3-4 nmoles per mg of DNA in both 24- and 45-h regenerating livers, being increased by probably 2-3-fold over normal. © 1969.