Thymidine kinetics in human lymphocyte transformation: determination of optimal labelling conditions.

The optimal conditions for assessing the rate of DNA synthesis by the incorporation of labelled thymidine in PHA-stimulated human lymphocytes were determined. Optimal labelling conditions could be sustained for only 3–4 hr. The exposure time was limited by both the failure to maintain saturating concentrations of exogenous thymidine and the deleterious affect of internal radiation. A linear incorporation of the label with time was not found to be a reliable criteria of optimal labelling conditions.