In vivo acute hematotoxicity of N,N'-bis[N-(2-chloroethyl)-N-nitrosocarbamoyl]cystamine (CNCC), a new nitrosourea analog

The in vivo hematotoxic effects on different hemopoietic cell compartments of a new nitrosourea analog CNCC were compared to another glycosidyl derivative, RFCNU. Bone marrow microenvironment in liquid culture, bone marrow and splenic colony-forming units in agar culture (GM-CFUc), relative spleen index, and spleen and bone marrow cellularity were evaluated in young adult (DBA/2 X C57B1/6)F1 mice. The drugs, dissolved in olive oil, were injected ip at either the minimal or the median or the maximal dose of the "maximally efficient dose range." A single administration of CNCC induced a dramatic depopulation of bone marrow and spleen within 12 and 24 hr and significantly reduced the GM-CFUc in both organs. A rapid recovery of both the total cell number and GM-CFUc was observed between Days 2 and 5 (kinetic experiment). The comparison of toxicity of 20 to 50 mg/kg CNCC and 15 to 30 mg/kg (2-chloroethyl)ribopyranosyl-3-nitrosourea RFCNU at Day 1 and Day 5 showed that the bone marrow microenvironment was modified by the effect of oil and was further impaired by CNCC in a concentration-dependent fashion. In contrast RFCNU had less effect on the microenvironment. Similarly, the bone marrow GM-CFUc population was reversibly impaired by CNCC in a dose-dependent fashion, and again RFCNU had less effect. In the spleen both drugs provoked a higher toxic effect than in the bone marrow; on Day 1 they decreased the GM-CFUc population by 1 to 2 log. On Day 5 a compensatory regeneration was obtained in all cases except the highest tolerable CNCC dose, whose effect was more delayed.