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Flashcards in Vitamin D Deck (25)
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1

vitamin D3 is also called

cholecalciferol

2

vitamin D3 is synthesized from

7-dehydrocholesterol

3

what are the two ways hydroxylation of vitamin D3 happens in the liver via 25-hydroxylase

1. microsomal cytochrome P-450 enzyme called CYP2R1
2. mitochondrial cytochrome P-450 enzyme called - CYP27A1

4

vitamin D3 -> 25-hydroxylase ->

calcidiol
25-hydroxycholecalciferol
25-OH cholecalciferol
25-OH vitamin D

5

how is vitamin D3 hydroxylated in the kidney via 1 alpha - hydroxylase

mitochondrial cytochrome P-450 enzyme called CYP27B1

6

vitamin D3 -> 1alpha-hydroxylase ->

calcitriol

7

____ is released from the kidney and bound to DBP in the blood

calcitriol

8

when sufficient amounts of calcitriol are present, the activity of ______ is decreased through negative feedback

1alpha-hydroxylase

9

_____ stimulates 1alpha-hydroxylase activity

PTH (parathyroid hormone)

10

_____ inhibits 1alpha-hydroxylase activity

FGF-23 (fibroblast like growth factor 23)

11

high concentrations of calcitriol stimulate

24-hydroxylase

12

calcitriol -> 24-hydroxylase ->

calcitetrol and calcitroic acid

13

vitamin D and calcitriol are NOT the same thing

T

14

_______ is a pleiotropic steroid hormone

calcitriol

15

calcitriol binds to a cell membrane VDR or a receptor called

MARRS (membrane associated rapid response steroid binding protein)

16

serum calcium homeostasis: calcitriol up regulates the transcription of the genes

TRPV6, calbindin D9K, Ca 2+ -ATPase, and claudins

17

in the kindey, calcitriol up-regulates the genes for BRUSH BORDER

TRPV5, calbindin D28K, and basolateral border Ca 2+ -ATPase

18

________ are responsible for bone resorption by releasing hydrochloric acid, alkaline phosphatases and collagenase which dissolve and catabolize the bone matrix

mature osteoclast

19

vitamin d deficiencies are linked to _____% of global annual death rate

60-65%

20

what 6 ways does calcitriol prevent cancer

1. * stimulates cell differentiation by stimulating E-cadherin *
2. inhibits cell proliferation by inhibiting oncogenes like Myc
3. promotes tumor cell apoptosis by activating caspases and bax
4. prevents tumor angiogenesis by inhibiting VEGF
5. increases NK cell activity
6. increases macrophage chemotaxic and phagocytic activity

21

why is prostate cancer and serum vitamin d related

dysfunctional prostate cells have down-regulated the production of the enzyme 1alpha-hydroxylase

22

______ regulates the expression and production of several cytokines (vitamin d and autoimmune)

calcitriol

23

_______ influence the immune system in a positive way and can further suppress the destructive activity of Th1 cells

Th2 cells and Treg cells

24

______ enhances calcium uptake and thus intracellular Ca 2+ concentrations

calcitriol

25

what is a toxic amount of vitamin d taken daily

50,000IU day/month