Aspects of Thymidine Metabolism and Function in Cultured Mammalian Cells Infected with Herpes Simplex Virus Type 1

We have investigated aspects of thymidine metabolism and function in cultured mammalian cells infected with herpes simplex virus under conditions in which virus DNA synthesis was either permitted, or was prevented by inhibiting the virus-induced DNA polymerase with phosphonoacetate. In 30 min pulse-labelling experiments the rates of [3H]thymidine transport into cells and its subsequent phosphorylation both reached maximum values about 6 h after infection. During the next 17 h these rates remained relatively constant in the absence of phosphono-acetate but declined to about 50 % of the 6 h value in the presence of this inhibitor. When the radioactive thymidine was present continuously throughout the infection the accumulated intracellular acid-soluble radioactivity reached maximum values at about 9 h. In the absence of phosphonoacetate this declined thereafter, but it remained relatively constant when virus DNA synthesis was prevented. This suggests some established equilibrium between the continuing entry of thymidine into cells and its subsequent removal by excretion. Excretion of thymidine-derived radioactivity was initially established by determining the fate of isotopically labelle