HNF 462 1st Edition Lecture 12Outline of Last LectureI. Forms of Vitamin AII. AbsorptionIII. StorageIV. TransportV. ExcretionVI. Functionsa. Eye sightb. Cellular Differentiation/Growth and DevelopmentVII. Deficiency and ToxicityVIII. ReproductionIX. SupplementsX. AssessmentXI. CancerOutline of Current LectureI. Food Sourcesa. Plantsb. AnimalsII. Formation of Vitamin D in the SkinIII. Activation of Vitamin D3IV. Absorption in the GutV. Cellular AbsorptionCurrent Lecture: Vitamin D1. Food Sourcesa. In Plants: (ex. in mushrooms) found naturally as D2, ErgocalciferolThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.b. In Animals Products: found naturally as D3, Cholecalciferol 2. Synthesis in the Skina. 7-dehydrocholesterol is absorbed in the skinb. When 7-dehydrocholesterol comes into contact with UV light (sun), will convert into pre-vitamin D3 c. Pre-vitamin D3 then spontaneously converts into Vitamin D3 (can take 1 hr or 1 day)d. Vitamin D3 then diffuses into the blood and binds to DBP (protein) for transport3. Activation of Vitamin D3a. Two organs involvedi. Liver hydroxylates at the 25-carbon position, then transported to kidneyii. Kidney hydroxylates at the 1-carbon positioniii. Active form of Vitamin D3 = 1,25-dihydroxyl D3iv. If there is too much of the active form in the system, then the kidney will begin to hydroxylate Vitamin D into its inactive form to maintain homeostasis4. Absorption in the Guta. No digestion required because vitamin D is not bound to anythingb. Absorbed via chylomicron transport because is a lipid soluble vitamin5. Cellular Absorptiona. Into the kidney bound to DBP as 25-hydroxyl D3b. Into other tissues as 1,25-dihydroxyl D3 bound to
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