A simplified method for measuring scheduled and unscheduled DNA synthesis in human fibroblasts

A simplified method for the rapid measurement of scheduled and unscheduled DNA synthesis in cultures of human fibroblasts is described. The use of cultures in which DNA synthesis is blocked by hydroxyurea (HU) together with those which are not blocked allows an estimation of the effect of chemicals on both types of DNA synthesis. This facilitates the interpretation of results and the selection of an optimum range of doses. Some results obtained with carcinogens and non-carcinogens are presented of the compounds so far tested. The methodology here described compares well in its validity with other more difficult and time consuming methods.