Effect of crystalline abrin on the biosynthesis of protein, RNA, and DNA in experimental tumors. (1970)

InstituteofBiochemistry,CollegeofMedicine,NationalTaiwanUniversity,Taipei,Taiwan,RepublicofChinaricinonthebiosynthesisofprotein,RNA,andDNA,aswellastheuptakeofaminoacidinthetumorcells.MATERIALSANDMETHODSAnimals.AdultmaleSwisswhite(NIH)mice,weighingfrom20to25g,andmalealbinoSprague-Dawleyrats,weighingfrom200to250g,wereusedfortransplantationoftumorcells.MaleLong-Evansrats,weighingfrom100to150g,wereusedforstudyingproteinbiosynthesisinratlivers.IsotopicCompounds.Thymidine-methyl-3Hwithaspecific@ activityof6.7Ci/mmole,uridine.2-'Cwithaspecificactivityof55.3mCi/mmole,L-leucine-4,5-3Hwithaspecificactivity@ of5Ci/mmole,uniformlylabeled Cwithaspecificactivityof250mCi/mole,andAIB2-3-'â€˜Cwithaspecificactivityof2.8mCi/mmolewerepurchasedfromNewEnglandNuclear,Boston,Mass.TheisotopiccompoundsweredilutedbeforeeachexperimentbydissolvingthemattheindicatedactivitiesinKrebs-Ringerphosphatebuffer.CrystaffineRicin.Ricinwasisolatedandcrystallizedasdescribed previously(11).ItwasdissolvedincoldKrebs-Ringerphosphatebuffertovariousconcentrationsforthefollowingexperiments.DeterminationofProtein.TheamountofproteinineachsamplewasquantitativelydeterminedbythephenolmethodofLowryetal. (12).Transplantation ofTumors.Tumortransplantation wascarriedoutbycollectingascitesfluidfromdonormicebearinga20-daygrowthofEhrlichascitestumororfromdonorratsbearinga5-daygrowthofYoshidaasciteshepatoma.Ehrlichascitesfluid(0.2ml)containing2Xi0'to4Xi07cellsand0.1mlofYoshidaascitesfluidcontaining7.5X106toiO@cellswith95%viability,asdeterminedbythetrypanbluedyeexclusionmethod,wereinjectedi.p.intorecipientmiceandrats,respectively.Incubation ofAscitesTumorCellswithIsotopicCompounds.Themethodsusedwerethesameasthosedescribedinthepreviousreport(7).Determination ofRadioactivity. ThefilterpaperdiscmethodwasusedfordeterminationofradioactivityoftheSUMMARYRicin,ahighlytoxiccrystallineproteinisolatedfromRicinuscommunis,hasastronginhibitoryeffectonproteinbiosynthesisandamoderateinhibitoryeffectonDNAbiosynthesisinEhrlichascitestumorandYoshidaasciteshepatoma cells.However,RNAbiosynthesis intheseneoplasticcellsisnotaffected.Theseinhibitoryeffectsarenotduetotheimpairmentofglucosemetabolismoroftheuptakeofaminoacidinthetumorcellsbyricin.Theproteinbiosynthesisofratliverismuchmoreresistanttoricinthanthatofneoplasticcells.INTRODUCTIONRicin,aphytotoxic protein,hasbeenpurifiedandcrystallizedfromR.communisinseverallaboratories(5,6,11).Inourearlierstudies,crystallinericinwastestedforitseffectonEhrlichascitestumor,andtheresultsindicatedthatricininhibitedthegrowthofEhrlichascitestqmorcompletelywhenasinglesublethaldoseofricinwasinjectedi.p.immediatelyafterinoculationofthetumorcells.Bymeasuringthetotalcellnumbersintheperitonealcavityofthericin-treatedmice,itwasdemonstratedthatwithin48hrricinreducedthecellnumberineachmousetolessthan10%oftheinjectedtumorcells.Theresultsindicatedthatncinexertedastrongcytolyticeffectonthetumorcells(9).RicinalsosuppressedthegrowthofEhrlichascitestumorcompletelywhen2sublethaldoseswereinjectedi.p.onthe3rdand4thdaysaftertumortransplantation. Ifthetreatmentwasinitiatedlaterthanthe4thdayaftertumortransplantation,ricinwasnotabletosuppressthegrowthofEhrlichascitestumorcompletely,butitdidprolongthelife-spanofthetreatedmiceconsiderably(10).Thepurposeofthisinvestigationwastostudytheeffectof