Table 2: Major in vivo and in vitro testing models for chromosome damage.
Test model |
Test guidance (Adopted) |
Design (taken from the OECD test guidance) |
Mammalian
chromosome aberration test |
OECD
TG 475 [39] - in vivo |
Animals
are exposed to the test substance (liquid or solid) by an appropriate route
of exposure and are sacrificed at appropriate times after treatment. Prior to
sacrifice, animals are treated with a metaphase-arresting agent. Chromosome
preparations are then made from the bone marrow cells and stained, and
metaphase cells are analysed for chromosome aberrations. Each treated and
control group must include at least 5 analysable animals per sex. The limit
dose is 2000 mg/kg/body weight/day for treatment up to 14 days, and 1000
mg/kg/body weight/day for treatment longer than 14 days. |
OECD
TG 473 [44] - in vitro |
The
in vitro chromosome aberration test
may employ cultures of established cell lines, cell strains or primary cell
cultures. Cell cultures are exposed to the test substance (liquid or solid)
both with and without metabolic activation during about 1.5 normal cell cycle
lengths. At least three analysable concentrations of the test substance
should be used. At each concentration duplicate cultures should normally be
used. At predetermined intervals after exposure of cell cultures to the test
substance, the cells are treated with a metaphase-arresting substance,
harvested, stained. Metaphase cells are analysed microscopically for the
presence of chromosome aberrations. |
|
Mammalian
micronucleus test |
OECD
TG 474 [46] - in vivo |
Animals
are exposed to the test substance by an appropriate route. Bone marrow and/or
blood cells are collected, prepared and stained. Preparations are analyzed for the presence of micronuclei. Each treated
and control group must include at least 5 analysable animals per sex.
Administration of the treatments consists of a single dose of test substance
or two daily doses (or more). The limit dose is 2000 mg/kg/body weight/day
for treatment up to 14 days, and 1000 mg/kg/body weight/day for treatment
longer than 14 days. |
OECD
TG 487 [48] - in vitro |
Cell
cultures of human or other mammalian origin are exposed to the test chemical
both with and without an exogenous source of metabolic activation. During or
after exposure to the test chemical, the cells are grown for a period
sufficient to allow chromosome damage or other effects on cell cycle/cell
division to lead to the formation of micronuclei in interphase cells. For
induction of aneuploidy, the test chemical should ordinarily be present
during mitosis. Harvested and stained interphase cells are analysed for the
presence of micronuclei. Ideally, micronuclei should only be scored in those
cells that have completed mitosis during exposure to the test chemical or
during the post-treatment period, if one is used. For all protocols, it is
important to demonstrate that cell proliferation has occurred in both the
control and treated cultures, and the extent of test chemical-induced
cytotoxicity or cytostasis should be assessed in
all of the cultures that are scored for micronuclei. |