The millipore filter assay technique for measuring tritiated thymidine incorporation into DNA in leucocyte cultures.

In this paper we present in detail the very rapid and sensitive Millipore filter assay technique for measuring tritiated thymidine incorporation during semiconservative DNA synthesis in human peripheral blood leucocyte cultures. Leucocytes which have been incubated with tritiated thymidine are trapped on a Millipore filter which is then suitably washed and dried. The filter is then immersed in scintillation fluid in a double-vial apparatus designed to ensure a reproducible counting geometry. Alternatively, the filter and its radioactive contents can be combusted to tritiated water, the radioactivity of which is then determined in a homogeneous counting system. The parameters related to the Millipore filter assay technique are presented, and its present uses and general applicability discussed.