Assessment of 5-fluorouracil and 4-nitroquinoline-1-oxide in vivo genotoxicity with Pig-a mutation and micronucleus endpoints.

Genotoxicity assessments were conducted on male Sprague Dawley rats treated with 5-fluorouracil (5-FU) and 4-nitroquinoline-1-oxide (4NQO) as part of an international validation trial of the Pig-a mutant phenotype assay. Rats were orally exposed to 0, 11.5, 23, or 46 mg/kg/day 5-FU for three consecutive days (Days 1-3); blood was sampled on Days -1, 4, 15, 29, and 45. Pig-a mutant phenotype reticulocyte (RETCD59-) and mutant phenotype erythrocyte (RBCCD59-) frequencies were determined on Days -1, 15, 29, and 45, and percent micronucleated reticulocytes (%MN-RET) were measured on Day 4. Rats were treated with 4NQO for 28 consecutive days by oral gavage, at doses of 1.5, 3, or 6 mg/kg/day. RBCCD59- and RETCD59- frequencies were determined on Days -1, 15, and 29, and MN-RET were quantified on Day 29. Whereas 5-FU was found to increase %MN-RET, no significant increases were observed for RBCCD59- or RETCD59- at any of the time points studied. The high dose of 4NQO (6 mg/kg/day) was observed to markedly increase RBCCD59- and RETCD59- frequencies, and this same dose level caused a weak but significantly elevated increase in MN-RET (approximately twofold). Collectively, the results provide additional support for the combination of Pig-a mutation and MN-RET into acute and 28-day repeat-dose studies. Environ. Mol. Mutagen. 55:735-740, 2014. (c) 2014 Wiley Periodicals, Inc.