Designation:E1262−88(Reapproved2013)StandardGuideforPerformanceofChineseHamsterOvaryCell/HypoxanthineGuaninePhosphoribosylTransferaseGeneMutationAssay1ThisstandardisissuedunderthefixeddesignationE1262;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thisguidehighlightssomeofthemorerelevantbio-logicalconceptsastheyarecurrentlyunderstood,andsumma-rizesthecriticaltechnicalaspectsforacceptablebioassayperformancesastheycurrentlyareperceivedandpracticed.TheChinesehamsterovarycell/hypoxanthineguaninephos-phoribosyltransferase(CHO/HGPRT)assay(1)2hasbeenwidelyappliedtothetoxicologicalevaluationofindustrialandenvironmentalchemicals.1.2Thisguideconcentratesonthepracticalaspectsofcellculture,mutagenesisprocedures,dataanalysis,qualitycontrol,andtestingstrategy.Thesuggestedapproachrepresentsaconsensusofthepanelmembersfortheperformanceoftheassay.Itistobeunderstood,however,thatthesearemerelygeneralguidelinesandarenottobefollowedwithouttheuseofsoundscientificjudgement.Usersoftheassayshouldevaluatetheirapproachbasedonthepropertiesofthesub-stancestobetestedandthequestionstobeanswered.1.3Deviationfromtheguidelinesbasedonsoundscientificjudgementshouldbynomeansinvalidatetheresultsobtained.1.4ThevaluesstatedinSIunitsaretoberegardedasstandard.Nootherunitsofmeasurementareincludedinthisstandard.1.5Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspriortouse.2.SignificanceandUse2.1TheCHO/HGPRTassaydetectsforwardmutationsoftheX-linkedhypoxanthine-guaninephosphoribosyltransferase(hgprt)locus(codingfortheenzyme,HGPRT)inChinesehamsterovary(CHO)cells.CellsoriginallyderivedfromChinesehamsterovarytissuearee...
