title: The relation of exposure time and drug concentration in their effect on cloning efficiency after incubation of human bone marrow with cytosine arabinoside.
abstract: The effect of different cytosine arabinoside (Ara-C) concentrations and exposure times upon clonogenicity of normal bone marrow cells was studied. One hour incubation, even at the pharmacologically high Ara-C concentration of 10(-5) M, was not cytotoxic. Prolonged incubation resulted in a very great increase in Ara-C cytotoxicity, provided that inactivation of Ara-C by deamination was limited. The results show that long-term exposure to Ara-C, even at pharmacologically very low concentrations, is deleterious to clonogenic cells and provide an experimental basis for the reported therapeutic efficacy of long-term low dose Ara-C administration in leukaemia and preleukaemic syndromes.
mesh_terms: D001853:Bone Marrow / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D002999:Clone Cells / Q000187:drug effects; D003114:Colony-Forming Units Assay; D003470:Culture Media; D003561:Cytarabine / Q000494:pharmacology*; D003584:Cytological Techniques; D004305:Dose-Response Relationship, Drug; D006801:Humans; D013997:Time Factors
chemical_list: D003470:Culture Media; D003561:Cytarabine