Pharmacological Glossary

DefinitionsofCommonlyUsedPharmacologicalTerms

AbsorbanceisusedforassayssuchasELISAassays,proteinandnucleicacidquantificationorenzymeactivityassays(i.e.intheMTTassayforcellviABIlity).AlightsourceIlluminatesthesampleusingaspecificwavelength(selectedbyanopticalfilter,oramonochromator),andalightdetectorlocatedontheothersideofthewellmeasureshowmuchoftheinitial(100%)lightistransmittedthroughthesample:theamountoftransmittedlightwilltypicallyberelatedtotheconcentrationofthemoleculeofinterest.

Anacronyminpharmacokineticsandpharmacologyforabsorption,distribution,metabolism,andexcretion,anddescribesthedispositionofapharmaceuticalcompoundwithinanorganism.

Adrugthatbindstoandactivatesareceptor.Canbefull,partialorinverse.Afullagonisthashighefficacy,producingafullresponsewhileoccupyingarelativelylowproportionofreceptors.Apartialagonisthaslowerefficacythanafullagonist.Itproducessub-maximalactivationevenwhenoccupyingthetotalreceptorpopulation,thereforecannotproducethemaximalresponse,irrespectiveoftheconcentrationapplied.Aninverseagonistproducesaneffectoppositetothatofanagonist,yetbindstothesamereceptorbinding-siteasanagonist.

Adrugthatbindstoareceptoratasitedistinctfromtheactivesite.Inducesaconformationalchangeinthereceptor,whichalterstheaffinityofthereceptorfortheendogenousligand.Positiveallostericmodulatorsincreasetheaffinity,whilstnegativeallostericmodulatorsdecreasetheaffinity.

Adrugthatattenuatestheeffectofanagonist.Canbecompetitiveornon-competitive,eachofwhichcanbereversIBLeorirreversible.Acompetitiveantagonistbindstothesamesiteastheagonistbutdoesnotactivateit,thusblockstheagonist"saction.Anon-competitiveantagonistbindstoanallosteric(non-agonist)siteonthereceptortopreventactivationofthereceptor.Areversibleantagonistbindsnon-covalentlytothereceptor,thereforecanbe"washedout".Anirreversibleantagonistbindscovalentlytothereceptorandcannotbedisplacedbyeithercompetingligandsorwashing.

Theareaundertheplasma(serum,orblood)concentrationversustimecurve.Itisusedintoxicology,biopharmaceuticsandpharmacokinetics.

Analbinostrainoflaboratorymousefromwhichanumberofcommonsubstrainsarederived.BALB/csubstrainsare"particularlywellknownfortheproductionofplasmacytomasoninjectionwithmineraloil,"animportantprocessfortheproductionofmonoclonalantibodies.Theyarealsoreportedashavinga"lowmammarytumourincidence,butdodevelopothertypesofcancersinlaterlife,mostcommonlyreticularneoplasms,lungtumours,andrenaltumours.

ThemaximumamountofdrugorrADIoligand,usuallyexpressedaspicomoles(pM)permgprotein,whichcanbindspecificallytothereceptorsinamembranepreparation.Canbeusedtomeasurethedensityofthereceptorsiteinaparticularpreparation.

C57BL/6oftenreferredtoas"C57black6"orjust"black6"isacommoninbredstrainoflabmouse.Darkbrown,nearlyblack,coat.Easilyirritabletemperament.Theyhaveatendencytobite.TheimmuneresponseofmicefromtheC57BL/6straindistinguishitfromotherinbredstrainslikeBALB/c.

ThecytochromeP450superfamily.ThefunctionofmostCYPenzymesistocatalyzetheoxidationoforganicsubstances.ThemostcommonreactioncatalyzedbycytochromesP450isamonooxygenasereaction.RH(organicsubstrate)+O2+2H++2e–→ROH+H2O.CYPfamiliesinhumansdividedamong18familiesofcytochromeP450genesand43subfamilies.

UsedtodeterminetheKivaluefromanIC50valuemeasuredinacompetitionradioligandbindingassay:
Where[L]istheconcentrationoffreeradioligand,andKdisthedissociationconstantoftheradioligandforthereceptor.

Areductioninresponsetoanagonistwhileitiscontinuouslypresentatthereceptor,orprogressivedecreaseinresponseuponrepeatedexposuretoanagonist.

(1)DrugMetabolismandPharmacokinetics;(2)DystrophiaMyotonicaProteinKinase.

Themolarconcentrationofanagonistthatproduces50%ofthemaximumpossibleresponseforthatagonist.

Invitroorinvivodoseofdrugthatproduces50%ofitsmaximumresponseoreffect.

Describesthewaythatagonistsvaryintheresponsetheyproducewhentheyoccupythesamenumberofreceptors.Highefficacyagonistsproducetheirmaximalresponsewhileoccupyingarelativelylowproportionofthetotalreceptorpopulation.Lowerefficacyagonistsdonotactivatereceptorstothesamedegreeandmaynotbeabletoproducethemaximalresponse(seeAgonist,Partial).

Enzyme-linkedimmunosorbentassay,alsoknownasanenzymeimmunoassay(EIA),isabiochemicaltechniqueusedmainlyinimmunologytodetectthepresenceofanantibodyoranantigeninasample.

Takingplaceoutsidealivingorganism.

Afirstopticalsystem(excitationsystem)illuminatesthesampleusingaspecificwavelength(selectedbyanopticalfilter,oramonochromator).Asaresultoftheillumination,thesampleemitslight(itfluoresces)andasecondopticalsystem(emissionsystem)collectstheemittedlight,separatesitfromtheexcitationlight(usingafilterormonochromatorsystem),andmeasuresthesignalusingalightdetectorsuchasaphotomultipliertube(PMT).Theadvantagesoffluorescencedetectionoverabsorbancedetectionaresensitivity,aswellasapplicationrange,giventhewideselectionoffluorescentlabelsavailabletoday.

Thesamplesinthemicroplateareexcitedusingpolarizedlight(insteadofnon-polarizedlightinFIandTRFmodes).Dependingonthemobilityofthefluorescentmoleculesfoundinthewells,thelightemittedwilleitherbepolarizedornot.

Achemicalcompoundthatproducesaresultinapreliminarybiochemicaltestindicatingthatthecompoundmeritsfurtherstudyaspartofadrugdiscoveryproject.

Inafunctionalassay,themolarconcentrationofanagonistorantagonistwhichproduces50%ofitsmaximumpossibleinhibition.Inaradioligandbindingassay,themolarconcentrationofcompetingligandwhichreducesthespecificbindingofaradioligandby50%.

Invitroorinvivodoseofadrugthatcauses50%ofthemaximumpossibleinhibitionforthatdrug.

Theequilibriumdissociationconstantforacompetitiveantagonist:themolarconcentrationthatwouldoccupy50%ofthereceptorsatequilibrium.

Thedissociationconstantforaradiolabeleddrugdeterminedbysaturationanalysis.Itisthemolarconcentrationofradioligandwhich,atequilibrium,occupies50%ofthereceptors.

Theinhibitionconstantforaligand,whichdenotestheaffinityoftheligandforareceptor.Measuredusingaradioligandcompetitionbindingassay,itisthemolarconcentrationofthecompetingligandthatwouldoccupy50%ofthereceptorsifnoradioligandwaspresent.ItiscalculatedfromtheIC50valueusingtheCheng-Prusoffequation.

Liquidchromatography-massspectrometry.ananalyticalchemistrytechniquethatcombinesthephysicalseparationcapabilitiesofliquidchromatography(orHPLC)withthemassanalysiscapabilitiesofmassspectrometry.TherearealotofmassanalyzersthatcanbeusedinLC/MS.SingleQuadrupole,TripleQuadrupole,IonTrap,TOF(timeofFlight)andQuadrupole-timeofflight(Q-TOF).

(1)acompoundthathasbeenselectedfromagroupofhitcompoundsbasedonqualitiessuchastheintensityofthebiochemicaleffectthatoccurswhenthecompoundispresent(efficacy),ortheabsenceofcoincidentaleffects(specificity); 
(2)achemicalcompoundthathaspharmacologicalorBIOLOGicalactivityandwhosechemicalstructureisusedasastartingpointforchemicalmodificationsinordertoimprovepotency,selectivity,orpharmacokineticparameters.

Thedifferencewithfluorescenceisthatthelightemittedbythesamplesistheresultofachemicalorbiochemicalreaction(insteadofbeingtheresultofexcitationbylight).Luminescenceplatereadersaresimpleropticallythanfluorescencereaders,astheydon"trequirealightsource,justalightdetector.Typically,theopticalsystemconsistsinalight-tightreadingchamber,andPMTdetectormeasuringthelightemittedbythesamplesduringthereaction.Commonapplicationsincludeluciferase-basedgeneexpressionassays,aswellascellviabilityandcytotoxicityassaysbasedontheluminescentdetectionofATP.

Alaboratorymousefromastrainwithageneticmutationthatcausesadeterioratedorabsentthymus,resultinginaninhibitedimmunesystemduetoagreatlyreducednumberofTcells.ThegeneticbasisofthenudemousemutationisadisruptionoftheFOXN1gene.Moststrainsofnudemiceareslightly"leaky"anddohaveafewTcells,especiallyastheyage.

Theproportionofradioligandthatisnotdisplacedbyothercompetitiveligandsspecificforthereceptor.Itcanbebindingtootherreceptorsorproteins,partitioningintolipidsorotherthings.

Theproportionofradioligandthatcanbedisplacedbycompetitiveligandsspecificforthereceptor.t½Thebiologicalhalf-lifeofadrugorradioligandinvitroorinvivo.Invitro,thet½oftheeffectofadrugisthetimetakenfortheresponsetoadrugtodeclinetohalftheoriginalresponse.Inradioligandbinding,thet½canbeusedtomeasurethedissociationrateofaradioligandfromitsreceptor,thereforeitisthetimetakenfortheamountofradioligandboundtothereceptorstodeclinetohalfitsoriginallevel.Invivo,t½referstothemetabolichalf-lifeofadrugorradioligand,i.e.thetimetakenfortheconcentrationofadruginplasmatodeclinetohalfitsoriginallevel.

Time-of-flightmassspectrometry(TOFMS)isamethodofmassspectrometryinwhichionsareacceleratedbyanelectricfieldofknownstrength.Thisaccelerationresultsinanionhavingthesamekineticenergyasanyotherionthathasthesamecharge.Thevelocityoftheiondependsonthemass-to-chargeratio.Thetimethatitsubsequentlytakesfortheparticletoreachadetectorataknowndistanceismeasured.Thistimewilldependonthemass-to-chargeratiooftheparticle(heavierparticlesreachlowerspeeds).Fromthistimeandtheknownexperimentalparametersonecanfindthemass-to-chargeratiooftheion.

Reliesontheuseofveryspecificfluorescentmolecules,calledlanthanides,thathavetheunusualpropertyofemittingoverlongperiodsoftime(measuredismilliseconds)afterexcitation,whenmoststandardfluorescentdyes(e.g.fluorescein)emitwithinafewnanosecondsofbeingexcited.Asaresult,itispossibletoexcitelanthanidesusingapulsedlightsource(Xenonflashlamporpulsedlaserforexample),andmeasureaftertheexcitationpulse.ThisresultsinlowermeasurementbackgroundsthaninstandardFIassays.

Atandemmassspectrometerconsistingoftwoquadrupolemassspectrometersinseries,witha(nonmass-resolving)radiofrequency(RF)onlyquadrupolebetweenthemtoactasacollisioncellforcollision-induceddissociation.Thefirst(Q1)andthird(Q3)quadrupolesserveasmassfilters,whereasthemiddle(q2)quadrupoleservesasacollisioncell.ThiscollisioncellisanRFonlyquadrupole(non-massfiltering)usinganinertgassuchasAr,HeorN2gastoprovidecollision-induceddissociationofaselectedprecursorionthatisselectedinQ1.SubsequentfragmentsarepassedthroughtoQ3wheretheymaybefilteredorscanned.

(sodium3´-[1-(phenylaminocarbonyl)-3,4-tetrazolium]-bis(4-methoxy-6-nitro)benzenesulfonicacidhydrate).Colorimetricassayforthenon-radioactivequantificationofcellproliferationandviability.TheassayisbasedonthecleavageoftheyellowtetrazoliumsaltXTTtoformanorangeformazandyebymetabolicactivecells.