维生素d缺乏性佝偻病（vitamin d deficiency rickets）课件

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1、VitaminDDeficiencyRicketsFanYangAssociatedProfessorPediatricDepartmentVitaminDVitaminDcomprisesagroupofsterolsVitaminD2=ergocalciferolCompletelysyntheticformproducedbytheirradiationoftheplantsteroidergosterolVitaminD3=cholecalciferolProducedphotochemicallybytheactiono

2、fsunlightorultravioletlightfromtheprecursorsterol7-dehydrocholesterolVitaminD=calciferolVITAMINDHumans&animalutilizeonlyvitaminD3&theycanproduceitinsidetheirbodiesfromcholesterol.Cholesterolisconvertedto7-dehydro-cholesterol(7DC),whichisaprecursorofvitaminD3.VITAMINDE

3、xposuretotheultravioletraysinthesunlightconvert7DCtocholecalciferol.VitaminD3ismetabolicallyinactiveuntilitishydroxylatedinthekidney&thelivertotheactiveform1,25Dihydroxycholecalciferol.1,25DHCactsasahormoneratherthanavitamin,endocrine¶crineproperties.VitaminD:TheS

4、unshineVitaminNotalwaysessentialBodycanmakeitifexposedtoenoughsunlightMadefromcholesterolintheskinFormationofVitaminDSkin(UVlight)7-dehydrocholesterolVitaminD3ErgosterolVitaminD2LiverOH-groupadded25-HydroxyvitaminD3Storageformofvitamin(~3monthsstorageinliver)KidneyO

5、H-groupaddedby1-hydroxylase1,25-dihydroxyvitaminD3ActiveformofvitaminD,a“steroidhormone”OH-groupaddedby24-hydroxylase24,25-dihydroxyvitaminD3InactiveformofvitaminD,readyforexcretionFUNCTIONSCalciummetabolism:vitaminDenhancescaabsorptioninthegut&renaltubules.Celldiffer

6、entiation:particularlyofcollagen&skinepitheliumImmunity:importantforCellMediatedImmunity&coordinationoftheimmuneresponse.VitaminD-FunctionsBonedevelopmentCalciumabsorption(smallintestine)Calciumresorption(boneandkidney)MaintainbloodcalciumlevelsPhosphorusabsorption(sm

7、allintestine)HormoneRegulationofgeneexpressionCellgrowthVitaminDFunctionsGroff&Gropper,2000VitaminDAffectsAbsorptionofDietaryCa1,25-(OH)2DbindstovitaminDreceptor(VDR)innucleusIncreaseincalbindin(Ca-bindingprotein)VitaminDAffectsAbsorptionofDietaryPhosphorus1,25-(OH)2

8、D3increasesactivityofalkalinephosphataseHydrolysesphosphateesterbondsReleasesphosphorusIncreaseinphosphatecarriersVitaminDd