A new in vivo gene mutation assay has been developed based on the phosphatidylinositol glycan anchor biosynthesis, Class A gene (Pig-a in rodents) as an endogenous reporter. Although a large number of chemicals have been evaluated in the rat Pig-a assay in 28-day repeat dose regimens, there was limited reporting of rat Pig-a assay after a single dose. A collaborative study by the Mammalian Mutagenicity Study group, which is a subgroup of the Japanese Environmental Mutagen Society, was conducted to verify the usefulness of the rat Pig-a assay after a single dose as a short-term genotoxicity test. As a part of this collaborative study, the in vivo mutagenicity of a single dose of pyrene (Pyr) was investigated in the red blood cell (RBC Pig-a assay) and in reticulocytes (PIGRET) of rats. Eight-week old male rats were orally dosed with Pyr at 500, 1000, and 2000 mg/kg or ethylnitrosourea (ENU) at 10 and 40 mg/kg as a positive control. The animals in each group were examined for Pig-a mutant frequencies (MF) except for animals in the 2000mg/kg group because of mortality or severe toxicity. The Pig-a MF in RBCs and reticulocytes, as CD59 negative cells, were evaluated once a week for 4 weeks after the dosing. With a single exposure to ENU, the Pig-a MF in both RBCs and reticulocytes increased in a time- and dose-dependent manner. In contrast, no statistically significant effect was observed in rats dosed with Pyr at 500 and 1000 mg/kg. Therefore, Pyr was concluded to be negative in the RBC Pig-a assay and the PIGRET assay after a single oral administration in rats. The result was consistent with previously reported Pig-a assays with repeat dose regimens.
Keywords: Gene mutation; Pig-a gene; Pyrene; Red blood cells; Reticulocytes.
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