INTRACELLULAR ACCUMULATION OF CYTOSINE-ARABINOSIDE IN MURINE NORMAL AND NEOPLASTIC LYMPHOCYTES FOLLOWING THEIR EXPOSURE TO SODIUM 2-MERCAPTOETHANESULFONATE

The effect of mesna on intracellular accumulation of cytosine arabinos ide (Ara-C) in murine normal and neoplastic lymphocytes was studied. S imultaneous exposure of cells to mesna at concentrations ranging from 0.25 to 1.0 mM and H-3-Ara-C (40.0 nM) resulted in a strong inhibition of Ara-C uptake in normal lymphocytes. Under the same experimental co nditions, mesna did not affect the Ara-C uptake in neoplastic cells (c ultured L5178Y mouse leukaemia cells and neoplastically transformed th ymus cells). It was found that the inhibitory effect of mesna was not cell cycle-dependent, since mesna reduced the Ara-C uptake in both nor mal quiescent and PHA-stimulated cells. We therefore concluded that me sna may selectively reduce Ara-C uptake by normal cells in vitro.