Drug sensitivity tests after cell separation on density gradients.

Cells from two leukaemic cell lines (K562 and L1210) were separated on a discontinuous Percoll gradient with densities from 1040 to 1090 by centrifugation. The cells recovered from gradient interfaces were checked for their DNA content and subjected to two different drug sensitivity tests using three cytostatic drugs. The purpose of the study was to compare the sensitivity of a sample of the whole population with that of the fractions thus obtained. Depending on the test used and the line tested, there was a 5.5 to 55.5% discordance between the results for the fractions and the non-separated cells.