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19 Cards in this Set

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What 2 things are regulated by Vit D?
1. Gene transcription
2. Ca2+/Phosphorus metabolism
What are the 2 dietary forms of Vitamin D?
1. Cholecalciferol (D3)
2. Ergocalciferol (D2)
What does the body use to synthesize Vitamin D?
7-dehydrocholesterol
What converts 7-dehydrocholesterol to cholecalciferol?
UV light in skin
Where does Cholecalciferol go after conversion from cholesterol?
To the liver
What happens to Vit D in the liver?
Conversion to active form
What is the active form of Vit D?
1,25-dihydroxy vitamin D
Where exactly does the activation of Vit D occur?
Hydroxylation #1: Liver (25)
Hydroxylation #2: Kidney (1)
What are the enzymes that hydroxylate Vit D during activation?
P450 cytochromes
What controls the synthesis of 1,25-dihydroxy Vit D in the kidney?
-PTH
-PO4 levels
What is the function of activated Vitamin D?
1. Binds VDR (receptor)
2. Heterodimerizes with RXR
What is RXR bound when it binds VDR?
9-cis-retinoic acid
What results from Vit D deficiency?
-Rickets in kids
-Osteomalacia in adults
What results from excess Vit D?
-Diarrhea, dermatitis,
-Headache, Bone Decalcifctn,
-Kidney/heart damage
-Retarded growth
-Kidney stones.
What do Vit D and PTH regulate?
Plasma calcium
What causes increased synthesis of active Vit D?
-Low plasma Calcium
-Increased PTH
What is Vit D used to treat?
Calcium deficiency and osteoporosis
How does Phosphate levels regulate Vit D synth?
When PO4 is low, it DECREASES PTH and increases Vit D
So what is Vit D involved in? (3 things)
1. Reg of genes for Ca/PO4
2. Reg of genes for immune system and epithel cell functn
3. Reg of hormone levels