November 4 notes - Summary of last lecture Vitamin D:...

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Summary of last lecture Vitamin D: mechanism of a steroid hormone Sources: diet (including fortification) and sun Forms of Vitamin D vitamin D 3 25-OH D 3 1,25-(OH) 2 D 3 Absorption, transport and excretion similar to lipids/cholesterol De novo synthesis of vitamin D
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Nomenclature Calciol (cholecalciferol, vitamin D 3 ) Parent compound No biological function Calcidiol (25-hydroxycholecalciferol, 25-OH D 3 ) Major plasma metabolite Index of status Calcitriol (1,25-dihydroxycholecalciferol, 1,25-(OH) 2 D 3 ) Active hormone Vitamin D-Binding Protein (DBP, transcalciferin) In plasma 194
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Cellular Mechanisms of Action of 1,25-(OH) 2 D 3 (Fig 10.14, 10.13) 1,25-(OH) 2 D 3 is lipid soluble acts like steroid hormone on tissues remote from production site at target tissues (intestine, bone and kidney to be studied), 1,25-(OH) 2 D 3 released from DBP and binds to receptor all target tissues for vitamin D contain either a cell membrane or a nuclear vitamin D receptor ( VDR ) for 1,25-(OH) 2 D 3 195
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196
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Genomic vs Non-Genomic Actions of 1,25-(OH) 2 D 3 (Fig 10.13) 1. Non-Genomic through signal transduction pathways linked to cell
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This note was uploaded on 07/06/2011 for the course BIOCHEM BIOCHEM 3N taught by Professor Macdonald during the Spring '11 term at McMaster University.

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November 4 notes - Summary of last lecture Vitamin D:...

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