Mammalian blood-mediated mutagenicity tests using a multipurpose strain of Escherichia coli K-12

Cytogenetic studies have been performed to determine the effect of 6-mercaptopurine (6-MP) on mammalian chromosomes in vivo. An elevated level of chromosome breakage is present in mouse bone marrow cells within 12 h after oral or parenteral dosing with 200 mg/kg. Damage is most severe at 24 h after oral dosing and at 72 h following intraperitoneal injection. A dose-response curve was constructed using oral doses of 10 to 200 mg/kg. The no-effect dose level lies within the 10–25 mg/kg range when administered as a single dose. In subacute studies, positive results have been obtained with as little as 2.5 mg/kg/day administered orally for 5 days.