An improved method for the mouse liver micronucleus test.

Abstract

We have developed a very practical method for performing the liver micronucleus test in mice. Using this method, we evaluated 11 different types of mutagens, including, 2-acetylaminofluorene, amsacrine, benzene, cyclophosphamide, diethylnitrosamine, 4-dimethylamino-3'-methylazobenzene, N-ethyl-N-nitrosourea, fluorouracil, mitomycin C, potassium chromate (VI) and selenious acid. In order to assess the sensitivity of our method, the peripheral blood reticulocyte micronucleus test was performed in the same mouse. Animals were given test chemicals once and underwent partial hepatectomy (PH) 24 h later in order to induce mitotic stimulation. Peripheral blood was sampled 0, 24, 48 and 72 h after treatment. The incidence of micronucleated hepatocytes was determined 5 days after PH. As a result, diethylnitrosamine and 4-dimethylamino-3'-methylazobenzene, known as liver carcinogens, increased the incidence of micronucleated cells in the liver only. Positive reactions for benzene, on the other hand, were found in the peripheral blood reticulocytes only. The other chemicals showed positive reaction in the liver and peripheral blood reticulocytes with almost the same maximum response of micronucleus induction. Our method was found to have the advantage over Cliets' liver micronucleus test in that it required much less time and was easier to perform procedures and highly sensitive in detecting clastogens. It can be used in combination with the peripheral blood reticulocyte micronucleus test to evaluate test chemicals in two tissues, the liver and the bone marrow, in the same animal. We propose a method of combining this test with the peripheral blood reticulocyte micronucleus test for efficient screening for the clastogenic potential of new chemicals in vivo.