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39 Cards in this Set
- Front
- Back
- 3rd side (hint)
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What is the most bioactive form of Vitamin D?
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1,25(OH)2D3
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What is the name of Provitamin D3?
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7,8-dehydrocholesterol
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What are the 3 sites of Vitamin D metabolism? (in order)
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Epidermal
Hepatic Renal |
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Describe epidermal metabolism of Vitamin D
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7,8-dehydrocholesterol is made into Previtam D3 via UV rays. Previtamin D3 is isomerized into Vitamin D3 via heat from sun.
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What does Vitamin D bind to?
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DBP (Vitamin D Binding Protein)
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What carries vitamin D from lymph system to circulatory system and then to the liver?
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Chylomicron
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Which 2 dietary sources do vitamin D come from?
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Meat = D3
Plant/fungal source = D2 |
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Where will carnivores get most of their Vitamin D from?
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Dietary sources
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Where will diurnal omnivorous reptiles get most of their Vitamin D from?
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Epidermal synthesis
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Primary source of hepatically metabolized Vitamin D is: free or bound Vitamin D3?
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Free
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What do the microsomes in liver do?
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Convert Vitamin D3 to other form of Vitamin D
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What's inside microsome?
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Enzymes
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Since PTH cant freely enter cell, what does it do?
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It acts on the promoter of 1a(OH)ase, which takes in the 25(OH)D3 and converts it to 1,25(OH)2D3
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What happens with bioactive form?
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It is released into circulation
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Some of the 1,25(OH)2D3 does not leave cell....what does it do?
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Inhibits PTH from going to receptor & starting the cascade of events
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How else does it inhibit the cascade?
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It inhibits 1a(OH)ase & stimulates the synthesis of 24(OH)ase, which makes 24,25(OH)2D3
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What does legumain do?
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Degrades DBP & frees Vitamin D3 in proximal tubule.
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What transports Vit D3 to mitochondria?
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IDBP-3
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What happens in the mitochondria?
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Bioactive form is produced
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What takes the bioactive form to the nucleus?
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IDBP-1
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What happens once it's in the nucleus?
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Production of 24(OH)ase increases and production of 1a(OH)ase decreases
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What does the bioactive form of Vitamin D3 bind to?
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VDR
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Which Vitamin D actions are rapid?
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Non-genomic actions
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Which Vitamin D actions are slow?
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Genomic actions
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What is Vitamin D's primary actin?
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To increase circulating calcium
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Which are the responsive tissues?
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Intestine, bone, PTH gland, kidney
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What does PTH do?
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Increases reabsorption calcium from the renal tubules and increases phosphate excretion from kidneys
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When does PTH levels increase?
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When calcium blood levels are low
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What does calcitonin do?
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Decreases reabsorption of calcium
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What does VDR do when it binds to VDR?
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VDR inhibits transcription of PTH
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What are the actions of 1,25(OH)2D3 in parathyroid?
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Increases VDR expression, increases CaSR , decreases parathyroid cell growth
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Most effective action in suppression of PTH is in concert with what?
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Calcium
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What do antigen presenting cells and T lymphocytes do?
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Possess VDR, synthesize 1a(OH)ase, and stimulates 24(OH)ase activity
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Vitamin D (analogs & metabolites) have most similar properties to:
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a. Minerals
b. Polypeptides c. Receptors d. Steroids |
Steroids
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>99% of circulating Vitamin D compounds compounds are protein bound, mostly to:
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a. Albumin
b. Chylomicron c. DBP d. Hemoglobin |
DBP
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Most active form of Vitamin D is:
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1a, 25-dihydroxyvitamin D3
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Which organ/tissue is primary site where Vitamin D is transformed to most bioactive form?
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Kidney
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Cellular effects of Vitamin D occur mostly via genomic actions or nongenomic actions?
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Genomic actions
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Not classic Vitamin D response tissue but falls in nonclassic system?
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a. Bone
b. Intestine c. Kidney d. Parathyroid e. Rennin-angiotensin system |
Rennin-angiotensin system
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