title: Interlaboratory Pig-a gene mutation assay trial: Studies of 1,3-propane sultone with immunomagnetic enrichment of mutant erythrocytes.
abstract: An international collaborative trial was established to systematically investigate the merits and limitations of a rat in vivo Pig-a gene mutation assay. The product of this gene is essential for anchoring CD59 to the plasma membrane, and mutations in this gene are identified by flow cytometric quantification of circulating erythrocytes without cell surface CD59 expression. Initial interlaboratory data from rats treated with several potent mutagens have been informative, but the time required for those flow cytometric analyses (∼20 min per sample) limited the number of cells that could be interrogated for the mutant phenotype. Thus, it was desirable to establish a new higher throughput scoring approach before expanding the trial to include weak mutagens or nongenotoxicants. An immunomagnetic column separation method that dramatically increases analysis rates was therefore developed (Dertinger et al. [2011]: Mutat Res 721:163-170). To evaluate this new method for use in the international collaborative trial, studies were conducted to determine the mutagenic response of male Sprague Dawley rats treated for 3 or 28 consecutive days with several doses of 1,3-propane sultone (1,3-PS). Pig-a mutant frequencies were measured over a period of several weeks and were supplemented with another indicator of genetic toxicity, peripheral blood micronucleated reticulocyte (MN-RET) counts. 1,3-PS was found to increase Pig-a mutation and MN-RET frequencies in both 3- and 28-day study designs. While the greatest induction of MN-RETs was observed in the 3-day study, the highest Pig-a responses were found with 28-days of treatment. Pig-a measurements were acquired in approximately one-third the time required in the original method, while the number of erythrocyte and reticulocyte equivalents analyzed per sample were increased by factors of 100 and 10, respectively. The data strongly support the value of using the immunomagnetic separation technique for enumerating Pig-a mutation frequencies. These results also demonstrate that the ongoing international trial will benefit from the inclusion of studies that are based on both acute and protracted repeat dosing schedules in conjunction with the acquisition of longitudinal data, at least until more data have been accumulated.
authors: Litron Laboratories, Rochester, New York, USA. sdertinger@litronlabs.com
authors: Stephen D
authors: SD
authors: Dertinger
authors: Souk
authors: S
authors: Phonethepswath
authors: Pamela
authors: P
authors: Weller
authors: Svetlana
authors: S
authors: Avlasevich
authors: Dorothea K
authors: DK
authors: Torous
authors: Jared A
authors: JA
authors: Mereness
authors: Steven M
authors: SM
authors: Bryce
authors: Jeffrey C
authors: JC
authors: Bemis
authors: Sara
authors: S
authors: Bell
authors: Susan
authors: S
authors: Portugal
authors: Michael
authors: M
authors: Aylott
authors: James T
authors: JT
authors: MacGregor
mesh_terms: D000818:Animals; D018957:CD59 Antigens / Q000235:genetics; D002138:Calibration; D003627:Data Interpretation, Statistical; D004305:Dose-Response Relationship, Drug; D023381:Endpoint Determination; D004912:Erythrocytes / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D005434:Flow Cytometry; D018189:Immunomagnetic Separation / Q000379:methods*; D007391:International Cooperation; D007753:Laboratories / Q000592:standards; D008297:Male; D008565:Membrane Proteins / Q000235:genetics*; D048629:Micronuclei, Chromosome-Defective / Q000139:chemically induced*; D015162:Micronucleus Tests / Q000379:methods / Q000592:standards; D009152:Mutagenicity Tests / Q000379:methods / Q000592:standards; D009153:Mutagens / Q000633:toxicity*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012015:Reference Standards; D015203:Reproducibility of Results; D012156:Reticulocytes / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D018570:Risk Assessment; D013876:Thiophenes / Q000633:toxicity*; D013997:Time Factors
chemical_list: D018957:CD59 Antigens; D008565:Membrane Proteins; D009153:Mutagens; D013876:Thiophenes; C080086:phosphatidylinositol glycan-class A protein; C003218:1,3-propane sultone