Clastogenicity and mutagenicity of hexavalent chromium in lacZ transgenic mice

The clastogenic and mutagenic effects of the hexavalent chromium compound K2CrO4 in lacZ transgenic mice (Muta Mouse) were investigated. Male Muta mice were administered an intraperitoneal dose of 40 mg/kg of K2CrO4 once on each of 2 consecutive days. The K2CrO4 induced a significant increase in the peripheral blood micronucleated reticulocyte count. Also, K2CrO4 induced a statistically significant increase in mutant frequency in the liver but not in the bone marrow on day 7 after the second treatment. The reason for the failure to increase the mutant frequency in the bone marrow may have been the rapid cell turnover rate there. The mutation induced by K2CrO4 in the bone marrow may have occurred in more differentiated cells than stem cells, and the rapid proliferative activity may have caused a rapid decrease in mutated cells by day 7. Further study with a sampling point earlier than day 7 is needed. The results obtained in the present study indicate that K2CrO4 has clastogenic and mutagenic potential in vivo.