The rodent bone marrow micronucleus assay: contrast between its sensitivity to human carcinogens and its insensitivity to NTP rodent carcinogens.

The rodent bone marrow micronucleus (MN) assay occupies a critical position in the accompanying schemes to detect potential human carcinogens and germ cell mutagens (Shelby, 1996; Ashby et al., 1996: for reviews of the MN assay see Heddle et al., 1983; Schlegel and MacGregor, 1984; CSGMT, 1990; Mavournin et al., 1990; Tinwell, 1990; Gatehouse, 1994; Asanami et al., 1995). The intention of this article is to note two perceptional problems currently associated with the MN assay. The first concerns how it should be used--as a screening assay, or as a means to evaluate the genetic toxicity in vivo of genotoxins defined in vitro. The second relates to its sensitivity to the rodent carcinogens defined by the US National Toxicology Program (NTP).