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12 Cards in this Set
- Front
- Back
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Pre-pro-PTH # of AAs
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115
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Pro-PTH # of AAs
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90
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PTH # of AAs
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84
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PTH Half-life
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-20 min
-rapidly cleaved by Kupfer cells in the liver |
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Region of biological effects of PTH
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1-34 AAs
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Calcium Sensor
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7-transmembrane receptor on the surface of chief cells of the parathyroid gland which monitors plasma calcium
low [Ca] -> increase in PTH secretion |
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Actions of PTH
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1. increases bone resorption and mobilizes calcium: pumps calcium into ECF
2. decreases plasma phosphate and increases urine phosphate excretion (phosphaturic action) 3. increases calcium reabsorption in distal tubules 4. increases formation of 1,25[OH]2D3 5. increases formation of osteoclasts (dominant) and osteoblasts |
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Receptor Activator of Nuclear Factor kappa-B Ligand (RANKL)
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-stimulated by PTH and 1,25[OH]2D3
-expressed on the surface of osteoblasts -interacts with RANK on pre-osteoclasts to promote maturation -depressed by estrogen |
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Receptor Activator of Nuclear Factor kappa-B (RANK)
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-expressed on the surface of pre-osteoclasts (monocytes)
-stimulated by RANKL on osteoblasts to promote maturation |
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Osteoprotegerin (OPG)
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-blocks RANKL
-regulates maturation of preosteoclasts -enhanced by estrogen (bone formation) -inhibited by cortisol (bone resorption) |
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Pulsatile PTH Injections
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sidesteps apoptosis of osteoblasts via prolonged PTH stimulation which activates bone formation and can be helpful for osteoporosis
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PTH Effect on Kidney
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1. increases calcium reabsorption in the distal nephron
2. inhibits reabsorption of phosphate in the proximal tubule 3. promotes hydroxylation of 25[OH]D3 |
