Relationship between thymidine transport and phosphorylation in Novikoff rat hepatoma cells as analyzed by a rapid sampling technique.
Incorporation of thymidine into Novikoff rat hepatoma cells was analyzed with a rapid sampling technique which allowed collection of 12 time points in 20 sec. Transport was a rapid, saturable, nonconcentrative process with a Km of about 85 micrometer. The intracellular thymidine pool was also rapidly labeled in cells which phosphorylated thymidine, that a group translocation process involving thymidine kinase can be ruled out. Under all conditions examined, phosphorylation, not the transport, of thymidine was the rate-determining step in its incorporation into the acid-soluble pool. Estimation of transport rates from total incorporation into cells which phosphorylate the substrate is invalid in this cell system and must be questioned in all instances.
D000255:Adenosine Triphosphate / Q000378:metabolism; D001693:Biological Transport, Active; D006528:Carcinoma, Hepatocellular / Q000378:metabolism*; D002460:Cell Line; D007700:Kinetics; D008113:Liver Neoplasms / Q000378:metabolism*; D008722:Methods; D013936:Thymidine / Q000378:metabolism*; D013942:Thymine Nucleotides / Q000378:metabolism*; D013997:Time Factors
D013942:Thymine Nucleotides; D000255:Adenosine Triphosphate; D013936:Thymidine