Endo-Ca and Pi homeostasis Flashcards

1
Q

PTH receptors (G-protein coupled Rs) are expressed in

A

bone and kidney

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2
Q

major hormones that regulate Ca homeostasis

A

Calcitriol
PTH
Calcitonin

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3
Q

PTH-R of bone expressed on

A

osteoblasts

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4
Q

Factors that inhibits Calcitriol synthesis via negative feedback

A

impacts on calcitriol synth:

High Vit D level
H. ECF Ca
H. ECF pi

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5
Q

Vit D impact on PTH

A

PTH secretion is inhibited by that

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6
Q

Calcitriol effect

A

inc. plasma conc of BOTH Ca and Pi

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7
Q

Ca salt content distribution in bone, ICF and ECF

A

99% in bone (hydrozyapetite crystals major form)

1% in ICF +ECF–> .1% ECF and 0.9 ICF

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8
Q

leads to decreased PTH secretion

A

an increase in plasma Ca

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9
Q

Which form of the Ca is affected by hypo and hypercalcemia

A

ionized form

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10
Q

Controls Ca2+ homeostasis

A

plasma Ca

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11
Q

DBP

transport protein

A

VitD-Binding protein

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12
Q

Cells with Ca-sensing plasma membrane R (Ca-R)

A

PTH-secreting cells
Calcitonin secreting cells
kidney and intestinal epithelium

Bone ? unclear

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13
Q

Calcitriol synth. stimulated by

A

impacts on Calcitriol synthesis:

PTH
L. ECF Ca
L. ECF Pi

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14
Q

T/F

ionized [Ca] pools in the ECF and ICF are at equilibrium

A

T

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15
Q

Rapid PTH responses of kidney cells expressing PTH-R

A

dec. Ca excretion with urine (within min)

Inc phosphate excretion with urine (within minutes)

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16
Q

PTH effect

A

inc Ca- dec Pi

17
Q

The calcium salt contents of:
Bone
Body fluids: ECF and ICF

A

Bone- 99%

Body fluid: 1% ( 0.1% ECF and 0.9% ICF)

18
Q

Percent distribution of calcitriol

A

99.6% and metabolites bound to Vit-D binding proteins (DBP)

and 0.4% as free form

19
Q

indirect PTH inhibition bu Vit D

A
  • feedback (through plasma conc of Ca)
20
Q

PTH secretion is regulated bu

A

ionized plasma Ca

21
Q

The active form of Vit D and its classification

A

Calcitriol

classified as steroid hormone

22
Q

Rapid Ca mobilization response to PTH

A

From Soluble form

23
Q

besides calcitriol, calcityonin and PTH what other hormones affect Ca homeostasis

A

glucocorticoids
thyroid H
GH
EST and And

24
Q

given Ca conc. is 10 mg/ dl

and pi is 4 mg/dl what are the %distributions of various forms

A

Ca: 50% ionized- 45% protein bound and 5% complexed with ions

Pi: 84% ionized (Free), 10% protein bound and 6% complexed with ions

25
Vit D
1,25 (OH)2D3- PTH inhibitor | PTH inhibition directly and indirectly
26
Vit D actions
are actions of it: Essential for acquiring adequate amounts of Ca2+ and Pi from the diet • Increasesplasma[Ca2+]andplasma[Pi] •Regulates processes of bone resorption and deposition (osteoblasts) • Inhibits PTH secretion
27
alkalemia
dec. ionized Ca
28
A common condition that results: inc. protein binding of Ca W/o affecting the total plasma conc. of Ca
Alkalosis
29
Hormones controlling the Ca/Pi homeostasis
PTH, Vit D, Calcitonin
30
VDR
a TF in target tissues: Small intestine, kidney, bone, PT gland
31
Direct PTH inhibition by Vit D D
by acting on paratyroid gland
32
Slow response of PTH-R expressing cells of the kidney | Which takes hours to days
stimulation of 1,25(OH)2D3 synthesis
33
Acidemia
inc inoized Ca
34
Slow Ca mobilization response of osteoblasts to PTH
via bone remodeling
35
Calcitonin
dec plasma level of both Ca and Pi
36
an increase in plasma concentration decreases PTH secretion via
Ca-sensing receptor mediated mechanisms
37
normal ranges of total plasma level pf Ca and Pi
Ca: 8.8- 10.3 mg/dl ~ 10 Pi: 2.5-4.5 mg/dl ~ 4
38
Nuclear vitamin D receptor
VDR
39
Alkalosis impact on plasma protein-bound Ca and ionized form
protein-bound Inc. ionized form decreases.