title: Compensatory erythropoiesis has no impact on the outcome of the in vivo Pig-a mutation assay in rats following treatment with the haemolytic agent 2-butoxyethanol.
abstract: The Pig-a assay has rapidly gained international interest as a useful tool for assessing the mutagenic potential of compounds in vivo. Although a large number of compounds, including both mutagens and non-mutagens, have been tested in the rat Pig-a assay in haematopoietic cells, there is limited understanding of how perturbations in haematopoiesis affect assay performance. Of particular concern is the possibility that regenerative haematopoiesis alone, without exposure to a genotoxic agent, could result in elevated Pig-a mutant cell frequencies. To address this concern, Wistar-Han rats were dosed by oral gavage with a non-genotoxic haemolytic agent, 2-butoxyethanol (2-BE). Dose levels ranging from 0 to 450 mg/kg were tested using both single administration and 28-day treatment regimens. Haematology parameters were assessed at minimum within the first 24h of treatment and 8 days after the final administration. Pig-a mutant frequencies were assessed on Days 15 and ~30 for both treatment protocols and also on Days 43 and 57 for the 28-day protocol. Even at doses of 2-BE that induced marked intravascular lysis and strong compensatory erythropoiesis, the average Pig-a mutant phenotype red blood cell and reticulocyte frequencies were within the historical vehicle control distribution. 2-BE therefore showed no evidence of in vivo mutagenicity in these studies. The data suggest that perturbations in haematopoiesis alone do not lead to an observation of increased mutant frequency in the Pig-a assay.
authors.affiliation: Pfizer Worldwide Research and Development, Genetic Toxicology, Eastern Point Road, MS-8274-1317, Groton, CT 06340, USA and Litron Laboratories, 3500 Winton Place, Rochester, NY 14623, USA michelle.o.kenyon@pfizer.com.
authors.forename: Michelle O
authors.initials: MO
authors.lastname: Kenyon
authors.affiliation: Pfizer Worldwide Research and Development, Genetic Toxicology, Eastern Point Road, MS-8274-1317, Groton, CT 06340, USA and Litron Laboratories, 3500 Winton Place, Rochester, NY 14623, USA.
authors.forename: Stephanie L
authors.initials: SL
authors.lastname: Coffing
authors.affiliation: Pfizer Worldwide Research and Development, Genetic Toxicology, Eastern Point Road, MS-8274-1317, Groton, CT 06340, USA and Litron Laboratories, 3500 Winton Place, Rochester, NY 14623, USA.
authors.forename: Joel I
authors.initials: JI
authors.lastname: Ackerman
authors.affiliation: Pfizer Worldwide Research and Development, Genetic Toxicology, Eastern Point Road, MS-8274-1317, Groton, CT 06340, USA and Litron Laboratories, 3500 Winton Place, Rochester, NY 14623, USA.
authors.forename: William C
authors.initials: WC
authors.lastname: Gunther
authors.affiliation: Litron Laboratories, 3500 Winton Place, Rochester, NY 14623, USA.
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Dertinger
authors.affiliation: Pfizer Worldwide Research and Development, Genetic Toxicology, Eastern Point Road, MS-8274-1317, Groton, CT 06340, USA and Litron Laboratories, 3500 Winton Place, Rochester, NY 14623, USA.
authors.forename: Kay
authors.initials: K
authors.lastname: Criswell
authors.affiliation: Pfizer Worldwide Research and Development, Genetic Toxicology, Eastern Point Road, MS-8274-1317, Groton, CT 06340, USA and Litron Laboratories, 3500 Winton Place, Rochester, NY 14623, USA.
authors.forename: Krista L
authors.initials: KL
authors.lastname: Dobo
mesh_terms: D000818:Animals; D004252:DNA Mutational Analysis; D004920:Erythropoiesis / Q000187:drug effects*; D005026:Ethylene Glycols / Q000633:toxicity*; D017930:Genes, Reporter; D053878:Hemolytic Agents / Q000633:toxicity*; D008297:Male; D008565:Membrane Proteins / Q000235:genetics*; D016296:Mutagenesis; D009152:Mutagenicity Tests; D009153:Mutagens / Q000633:toxicity*; D009154:Mutation; D017208:Rats, Wistar; D012156:Reticulocytes / Q000187:drug effects
chemical_list: D005026:Ethylene Glycols; D053878:Hemolytic Agents; D008565:Membrane Proteins; D009153:Mutagens; C080086:phosphatidylinositol glycan-class A protein; C017096:n-butoxyethanol