HormonesIntroductionofhormonesHormoneHierarchyofActionHormoneMechanismsofActionExamples shifeng:IntroductionofHormonesWhatisahormonesClassificationofhormonesDifferencesbetweenanimalhormonesandplantshormonesFunctionofhormonesHeterogeneityofsignalshormonesneurotransmitters(神經(jīng)傳遞素)growthfactorsmetabolitessecondmessengersdrugslightTheConceptofHormonesA

hormoneisasubstancethatissynthesizedandsecretedbyspecializedcellsandcarriedviathecirculationtotargetcells,whereitelicitsspecificchangesinthemetabolicbehaviorofthecellbyinteractingwithahormone-specificreceptor.InsulinisthefirsthormonediscoveredInsulin

smallpeptidehormone–51aminoacidsproducedinpancreaticbetacellshighglucoselevelsinducesecretionmajorsitesofactionareliver,muscleandadiposetissueActionsofinsulinBiologicalEffectsofInsulinAminoaciduptakeinmuscleDNAsynthesisGeneexpressionProteinsynthesisNa+/K+pumpGrowthresponseGlucoseuptakeinmuscleandadiposetissueLipolysisLipogenesisinadiposetissueandliverGlucoseglycogeninliverandmuscleGluconeogenesisInliverEffectofinsulinintargettissuesTissueActivationInhibitionLiverGlycogenesisLipogenesisGluconeogenesisKetogenesisAdiposetissueGlucoseuptakeLipogenesisLipolysisMuscleGlycogenesisGlucoseuptakeAminoaciduptakeProteindegradationInsulinisthefirsthormonediscoveredInsulinissecretedbygroupsofcellswithinthepancreascalledisletcells.(Thepancreasisanorganthatsitsbehindthestomachandhasmanyfunctionsinadditiontoinsulinproduction.Thepancreasalsoproducesdigestiveenzymesandotherhormones.)Insulinisapeptidehormonethatfunctionsinloweringbloodglucoselevels.Insulinhasseveralactivitiesthatplishthisgoal,summarizedbelow:1.Insulininhibitstranscriptionoftheenzymephosphoenolpyruvatecarboxykinase(PEPCK).PEPCKisakeyenzymeingluconeogenesisandtranscriptionistheprimarymeansofregulatingit.ByinhibitingPEPCKtranscription,insulincandepressglucoseproductiontremendously.(Conversely,thehormoneglucagon,whichincreasesbloodglucoselevels,stimulatesPEPCKtranscription.)2.Insulinstimulatestranslocationoftheglucosetransporterproteinfromcytosoltothecellsurface.Glucosetransportproteincarriesoutthefacilitatedtransportofglucose.3.Insulin

stimulatesphosphataseactivitywhichremovesphosphatesfrommoleculesactivatedbythekinasecascade.Thus,insulinopposestheeffectsofglucagonandepinephrineInsulinissynthesizedasapreprohormoneinthebcellsoftheisletsofLangerhans.ItssignalpeptideisremovedinthecisternaeoftheendoplasmicreticulumanditispackagedintosecretoryvesiclesintheGolgi,foldedtoitsnativestructure,andlockedinthisconformationbytheformationof2disulfidebonds.Specificproteaseactivitycleavesthecenterthirdofthemolecule,whichdissociatesasCpeptide,leavingtheaminoterminalBpeptidedisulfidebondedtothecarboxyterminalApeptide.Insulinalsostimulatesfattyacidbiosynthesisasfollows:1.Insulinfavorsentryofglucoseintocells,which,inturn,favorsproductionofNADPHviaentryofglucose-6-phosphateintothepentosephosphatepathway.2.Insulinactivatesthepyruvatedehydrogenasecomplex,whichfavorsproductionofacetyl-CoA.3.Insulintendstoreversetheeffectsofthekinasecascade,andstimulatesdephosphorylationofacetyl-CoAcarboxylase,whichfavorspolymerizationoftheenzymeinanactiveform.Regulationoffattyacidsynthesisinanimalcells,suchaslivercells.

Aspectsofthecontrolofbloodglucoselevelsbypancreaticsecretionofinsulinandglucagon

Actionsofglucagoninliverthatleadtoariseinbloodglucose.

DiscoveredthatGTPbindingproteinsactassignaltranducersbetweenthe“discriminator”andthesignal“amplifier”.DemonstratedtheroleofGproteinsusingamutatedleukemiacellline.ClassificationofHormones1.Fromsource:Animalhoemonesplanthoemones2.Fromchemicalcomponent:peptidesorpolypeptides,suchas

insulinorglucagonsteroid,includingglucocorticoidsandthesexhormonesaminoacidderivatives,includingthecatecholaminesandthyroxine.DifferencesbetweenanimalhormonesandplantshormonesHormoneswerefirstdescribedinanimalsystems.Theyarechemicalsignallingmoleculesormessengers,whicharesynthesisedinglands.Thesechemicalmessengersaretransportedaroundthebodyandactontissuesatadistancefromtheglandinwhichtheywereproduced.Animalhormonesalsohaveveryspecificeffectsonspecifictissues.Planthormonesarenotproducedinglands(buttheyaretransportedaroundtheplanttoactondistanttissues).Planthormonesarenotspecificintheiraction.Ormoresimply,theycanproducedifferentresponsesindifferenttissues.Planthormonesaresmall,simplemoleculesbutanimalhormonesarelarge,complexmoleculesTherearemanytypesofanimalhormonesbutthereareonlyfiveclassicalplanthormonesandtheseare:gibberellins,abscisicacid,ethylene,auxinscytokinins.Ethyleneisunusualbecauseitisagas.Planthormonesarealsoknownasplantgrowthsubstancesorplantgrowthregulators.EndocrineSystemEndocrineSystemCommonVertebrateHormonesPituitaryHormonesHypothalamicHormonesThyroidHormonesParathyroidHormoneDigestiveHormonesPancreaticHormonesPlacentalHormonesGonadalHormonesAdrenalCorticalHormonesAdrenalMedullaryHormonesLiverHormonesKidneyHormonesCardiacHormonesPinealHormonesPituitaryHormones（垂體激素）PituitaryHormonesHypothalamicHormones

(下丘腦激素)甲狀腺激素甲狀旁腺激素DigestiveHormones（消化道激素）DigestiveHormones（消化道激素）PancreaticHormones（胰腺激素）PlacentalHormones(胎盤(pán)激素)GonadalHormones(性腺激素)AdrenalCorticalHormones

（腎上腺皮質(zhì)激素）AdrenalMedullaryHormones

（腎上腺髓質(zhì)激素）LiverHormones（肝臟激素）KidneyHormones(腎臟激素)Cardiac

Hormones(心臟激素)Pineal

Hormones（松果體激素）TheEndocrine(orHormonal)SystemisInvolvedwithAging?

Yes!TheEndocrineSystemdirectlycontrolstheprocessofaging,includinghowfastorslowwewillageandhowhealthywewillbeintheprocess.ThroughthedirectionsoftheEndocrineSystem,itshormonesactuallyguidethebodyinitsdailymetabolicfeats.HormonesmanufacturedbytheEndocrineSystemdirectlygovernthewelfareofourwholebody,keepingusyoung,healthyandhappy.Hormonescanhelpusdelaytheagingprocessandkeepusgenerallyfreefromdisease.KeyConceptsTheendocrinesystemincludesseveralglandsandscatteredcellsandthehormonestheysecreteintothebloodstream.Ahormoneexertsaspecificphysiologicaleffectontargetcells,whichhavereceptorsforit.Exocrineglandsdeliversubstancesintoducts,whichopenontobodysurfaces.2.Thenervousandendocrinesystemsinteracttomaintainhomeostasis.Thenervoussystemactsfasterandmorelocallythantheendocrinesystem.Neurosecretorycells,whichareneuronsthatsecretehormones,areaphysicalandevolutionarylinkbetweenthetwosystems.3.Diversespecieshavehormonelikeregulation,andmanyusethesignalingmoleculecAMP.4.Thegastrointestinaltractsecretesseveralhormonesthatregulatedigestion.Inmammals,theatriumoftheheartsecretesatrialnatriuretichormone,whichregulatesbloodpressure,bloodvolume,andtheexcretionofsodiumions,potassiumions,andwater.

Pheromones(信息素)arehormonelikebiochemicalsignalsbetweenindividuals.5.Peptidehormonesarewatersolubleandbindtothesurfacereceptorsoftargetcells,stimulatingconversionofATPtocAMPontheinnerfaceofthecellmembrane.ThecAMPthentriggersaspecificmetaboliceffect.Thelipid-solublesteroidhormonescrosstargetcellmembranes,bindreceptorsinthecytoplasmornucleus,andactivategenestodirectsynthesisofproteinsthatprovidethecell'sresponse.Inanegativefeedbackloop,excessofahormoneortheproductofahormone-inducedresponsesuppressesfurthersynthesisorreleaseofthathormoneuntillevelsreturntonormal.Inapositivefeedbackloop,thehormonecausesaneventthatincreasesitsproduction.Ionsornutrientlevelsneartheendocrinecells,inputfromthenervoussystem,andotherhormonescontrolfeedbackloops.7.

Simplerinvertebratesmayhaveonlyneurosecretorycells.Morecomplexinvertebrateshaveinteractinghormones.Changinglevelsofjuvenileandmoltinghormonecontrolinsectmetamorphosis.

Thesamehormonesmayfunctiondifferentlyindifferentvertebratespecies.Reproductivecyclesarehormonallycontrolledandarediverse.Theendocrinesystemfunctionsinahierarchy.Thehypothalamusproducesreleasinghormones,whichtravelinneurosecretorycellstotheanteriorlobeofthepituitarygland.Theretheystimulatereleaseofanteriorpituitaryhormones.Thehypothalamusalsomanufacturestwohormonesthatarestoredinandreleasedfromtheposteriorlobeofthepituitarygland---antidiuretichormoneandoxytocin.Inmanyvertebratespecies,theregionbetweentheanteriorandposteriorlobesofthepituitarysecretesmelanocyte-stimulatinghormone,whichcolorsskin.PlantHormonesAuxins（植物生長(zhǎng)素）

Gibberellins(赤霉素)Cytokinins（細(xì)胞分裂素）

AbscisicAcid（脫落酸）

Ethylene（乙烯）Auxins（植物生長(zhǎng)素）Auxinspromotestemelongation,inhibitgrowthoflateralbuds(maintainsapicaldominance).Theyareproducedinthestem,buds,androottips.Example:IndoleAceticAcid(IA，吲哚乙酸).Tryptophan.....................Indolaceticacid(auxin)Gibberellins(赤霉素)Likeauxin,Gibberellinspromotestemelongation.Gibberellinactsasachemicalmessenger,hormone,tostimulatethesynthesisofenzymessuchasa-amylaseandotherhydrolyticenzymesimportantduringgerminationofseedlingsinordertoinsurereleaseofstorednutrients.

Theyarenotproducedinstemtip.Gibberellicacidwasthefirstofthisclassofhormonetobediscovered.Cytokinins（細(xì)胞分裂素）Cytokininsstimulatecelldivisionanddifferentiationinplants;usuallycoupledwithauxin.Cytokininsretardsenescence(aging).Theyareproducedingrowingareas,suchasmeristemsattipoftheshoot.Zeatinisahormoneinthisclass,andoccursincornAbscisicAcid（脫落酸）ABAinduceswinterdormancybysuppressingmRNAproduction.WithoutmRNAauxinandgibberellinsarenolongerproduced.AbscisicAcidpromotesseeddormancybyinhibitingcellgrowth.Itisalsoinvolvedinopeningandclosingofstomataasleaveswilt.ABAentersguardcellsduringperiodsofwaterstress,andbringsabouttheoutwardtransportofpotassiumions(K+).Ethylene（乙烯）Ethyleneisagasproducedbyripefruitsfromtheaminoacidmethionine.Ethyleneisusedtoripencropsatthesametime.Sprayedonafielditwillcauseallfruitstoripenatthesametimesotheycanbeharvested.Ethylene（乙烯）EthylenecontrolstheripeningoffruitsDuringtheinitialgrowthofaseedling,ethyleneappearstoberesponsibleforthehookedshapeofthedevelopingshoot.Thishelpsprotecttheyoungtenderleavesfromthewearandtearofgrowingupthroughthesoil.Ethylenemayinsurethatflowersarecarpelate(female)whilegibberellinconfersmalenessonflowersEthylenepromotestheproductionofcellulasespriortoleaffallandabscission.SeedgerminationHormoneHierarchyofActionHormonalregulationinvolvesahierarchyofcelltypesactingoneachothereithertostimulateortomodulatethereleaseandactionofahormone.SecretionofhormonesfromendocrinecellsisstimulatedbychemicalsignalsfromregulatorycellsthatoccupyahigherpositioninthishierarchyThehierarchicalnatureofhormoneaction

1.Hormonalactioniscontrolledultimatelybythecentralnervoussystem,whichtransmitssignalstothehypothalamus.Itrespondsbyproducingfactorsthateitherstimulate(calledreleasingfactors)orinhibitthereleaseofhormonesfromthepituitary.2.Pituitaryhormonesdooneofthefollowing:a.Theystimulateotherendocrineglands,eachofwhichreleasesahormonethatactsonatargettissueandelicitsaspecificmetabolicresponse.b.Alternatively,theyactdirectlyonatargettissue.Theactionofahormonesetsinmotioneventsthatultimatelylimitthataction.Somepituitaryhormonesstimulatetargettissuedirectly.Forexample,prolactinstimulatesmammaryglandstoproducemilk.Mostpituitaryhormonesactonendocrineglandsthatoccupyanintermediate,orsecondary,positioninthehierarchy,stimulatingthemtoproducehormonesthatexerttheultimateactionsontargettissues.Pituitaryhormonesthatactonotherendocrineglandsarecalledtropichormonesortropins.Theactionofahormoneisself-limitingbecauseoftheexistenceoffeedbackloops,inwhichsecretionofahormonesetsinmotionaseriesofeventsthatleadstoinhibitionofthatsecretionTransmissionandinhibitioninneuralnetworks

HormoneMechanismsofAction1.Enzymeactivationorinhibitionviasecondmessengers;2.Stimulationofthesynthesisofparticularproteins,throughactivationofspecificgenes;3.Selectiveincreasesinthecellularuptakeofcertainmetabolites.Amongthislastcategoryaresomereceptorsthatservedirectlyasionchannels,withhormonebindingcausingaconformationalchangethatopensthechannel,andotherreceptorsthatstimulateuptakebystill-unknownmechanisms.Mosthormonesinteractingwithintracellularreceptorsexerttheireffectsbycontrollingratesoftranscriptionofspecificgenes.Inthiscase,thehormonebindstoareceptorandthecomplexmigratestothenucleus,whereitinteractswithspecificDNAsites.

Hormonesinthisclassincludesteroids,thyroidhormones,andthehormonalformsofvitaminD.Inaddition,retinoids,derivedfromretinoicacid(relatedtovitaminA),exertregulatoryeffectsinembryonicdevelopmentthroughinteractionswithintracellularreceptors.Mechanismsofhormonesthatactthroughmembrane-boundreceptorsthatinteractwithGproteinsorthathavecatalyticdomainsonthecytoplasmicside,aresummarizedinbelow.Signaltransductionpathway

involvingadenylatecyclase.Signaltransductionpathwaysinvolvingphosphoinositideturnover.Eukaryoticsignaltransductionsystemsinvolvingmembranereceptors(1-5)and/orsecondmessengers(1-4)..Theendresultofmostinteractionsbetweenahormoneandamembranereceptorisactivationofoneormoreproteinkinases,whetherornotasecondmessengerisinvolved.Morethan100differentproteinkinaseshavebeendescribedinvertebratecells,allofthemrelated,asdeterminedbyaminoacidsequencehomologies.Morerecentworkisuncoveringahostofspecificproteinphosphatases,alsosubjecttocontrolbycellsignalingmechanisms.KinaseCascade1.Stimulusforphosphorylationishormoneinteraction(glucagonorepinephrine)withacellularreceptor,whichsendsasignalviaaGproteintothemembrane-boundenzyme,adenylatecyclase.2.Adenylatecyclase,inturn,formscAMPfromATP.3.cAMPactivatescAMP-dependentproteinkinase.Itoperatesasfollowsinthecell:

4.cAMP-dependentproteinkinasephosphorylatesphosphorylasebkinase.5.Phosphorylasebkinasephosphorylatesglycogenphosphorylasebtoconvertittoglycogenphosphorylasea.6.Glycogenphosphorylaseacatalyzesphosphorolysisofglycogentoformglucose-1-phosphate.acascadeofenzyme-catalyzedreactions.Epinepherineandglucagonsignalslowbloodglucoselevel;Adenylatecyclaseisactivatedbythebindingofthehormonestoreceptors;cAMPactivatestheproteinkinaseA,whichphosphorylatesandactivatethelipase.RegulatorycascadesaffectingglycogensynthesisandmobilizationTheregulatorycascadecontrollingglycogen