In vivo toxicity of 3'-azido-3'-deoxythymidine (AZT) on CBA/Ca mice.

CBA/Ca male mice were given 3'-azido-3'-deoxythymidine (AZT) in drinking water (1 mg/ml) for up to 7 weeks. Water consumption and body weight decreased significantly. Neutropenia and lymphopenia were observed during and after exposure. Significant macrocytic anemia developed and disappeared as a function of red cell life span after stopping AZT intake. A microthrombocytosis was seen. Bone marrow cellularity and spleen colony-forming unit (CFU-s) content fell, but recovered completely and quickly after terminating AZT intake. Hemopoietic stem cell function measured by 2 different methods of rescuing fatally irradiated mice was normal 4 weeks after AZT exposure, suggesting that AZT treatment does not induce a long-lasting effect in genetic control of mitotic potential of stem cells. This is in marked contrast to exposure of CBA/Ca mice to benzene and ionizing radiation.