Effect of cell density on intracellular adriamycin concentration and cytotoxicity in exponential and plateau phase EMT6 cells.

The relationship between cell number and available Adriamycin (ADM) has been investigated in EMT6 cells. Results have shown that the ratio between cell number and total available ADM is important in determining in vitro ADM uptake and surviving fraction. Having established this effect, the sensitivity of exponentially growing and plateau phase EMT6 cells to ADM was investigated. ADM was assayed by extraction followed by spectrofluorimetry and also by flow cytometry (FCM); both methods were found to give the same ratio of intracellular ADM between exponentially growing and plateau phase cells. We found that for a given exposure dose plateau phase cells were more sensitive than exponentially growing cells. For the same dose per cell, plateau cells take up more ADM than exponentially growing cells. But for a given intracellular ADM concentration exponentially growing cells have a lower surviving fraction than plateau phase cells. We conclude that the surviving fraction is dependent on the proliferative state of the cells and in order to draw that conclusion it is important to relate the ADM effect on cells in vitro to the total ADM available to each cell.