Lucanthone modification of cyclophosphamide toxicity in the Chinese hamster

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The interaction of lucanthone and cyclophosphamide (CYC) was investigated in the Chinese hamster in terms of the LD 50 7 and LD 50 30 . These values may be indicative of gastrointestinal stem cell depletion and bone marrow stem cell depletion, respectively. When a nonlethal dose of 100 mg/kg lucanthone preceded CYC injection, the LD 50 7 for CYC reached its minimum value of 470 mg/kg at a treatment interval of 10 hours. Lucanthone administered simultaneously with CYC had no effect on the control LD 50 7 of 750 mg/kg, and by 48 hours after lucanthone administration the LD 50 7 had returned to the control value. When CYC administration preceded that of lucanthone, the LD 50 7 reached a minimum of value of 610 mg/kg at an interval of 5 hours; however, for the entire sequence it was approximately 6411 mg/kg over all intervals up to 48 hours. The LD 50 30 for CYC was only slightly reduced by the presence of lucanthone, indicating that bone marrow sensitivity to CYC was only marginally affected by lucanthone. These data indicate that lucanthone may interact with CYC damage in much the same way as it interacts with radiation damage, viz, by reducing cellular capacity to accumulate and repair sublethal damage.