The influence of monocyte (adherent cell) content in human mononuclear blood cell populations on the estimation of individual levels of N-acetoxy-2-acetylaminofluorene induced unscheduled DNA synthesis.

Human mononuclear blood cells were isolated from heparinized blood samples by centrifugation in Isopaque-Ficoll gradients. The isolated mononuclear cells were then subjected to further fractionation according to size by sedimentation at unit gravity. The faster sedimenting cells containing high proportions of monocytes were 2-fold greater at carrying out N-acetoxyl-2-acetylaminofluorene (NA-AAF) induced unscheduled DNA synthesis (UDS) than were cell fractions containing only lymphocytes. Furthermore, the mononuclear cell populations that adhere to plastic surfaces were shown to be responsible for the increased NA-AAF induced UDS observed for the cells that sediment at a faster rate in a unit gravity gradient. Interindividual fluctuations in NA-AAF induced UDS estimated on mononuclear blood cells could not be explained in terms of fluctuations in adherent cell (monocyte) NA-AAF induced UDS when the general population was examined. These data support the notion that although monocytes have a greater DNA repair synthesis, the variation in monocyte content and/or function encountered in the general population is not great enough to seriously affect interindividual comparisons of NA-AAF induced UDS.