Endo-Ca and Pi homeostasis Flashcards
PTH receptors (G-protein coupled Rs) are expressed in
bone and kidney
major hormones that regulate Ca homeostasis
Calcitriol
PTH
Calcitonin
PTH-R of bone expressed on
osteoblasts
Factors that inhibits Calcitriol synthesis via negative feedback
impacts on calcitriol synth:
High Vit D level
H. ECF Ca
H. ECF pi
Vit D impact on PTH
PTH secretion is inhibited by that
Calcitriol effect
inc. plasma conc of BOTH Ca and Pi
Ca salt content distribution in bone, ICF and ECF
99% in bone (hydrozyapetite crystals major form)
1% in ICF +ECF–> .1% ECF and 0.9 ICF
leads to decreased PTH secretion
an increase in plasma Ca
Which form of the Ca is affected by hypo and hypercalcemia
ionized form
Controls Ca2+ homeostasis
plasma Ca
DBP
transport protein
VitD-Binding protein
Cells with Ca-sensing plasma membrane R (Ca-R)
PTH-secreting cells
Calcitonin secreting cells
kidney and intestinal epithelium
Bone ? unclear
Calcitriol synth. stimulated by
impacts on Calcitriol synthesis:
PTH
L. ECF Ca
L. ECF Pi
T/F
ionized [Ca] pools in the ECF and ICF are at equilibrium
T
Rapid PTH responses of kidney cells expressing PTH-R
dec. Ca excretion with urine (within min)
Inc phosphate excretion with urine (within minutes)
PTH effect
inc Ca- dec Pi
The calcium salt contents of:
Bone
Body fluids: ECF and ICF
Bone- 99%
Body fluid: 1% ( 0.1% ECF and 0.9% ICF)
Percent distribution of calcitriol
99.6% and metabolites bound to Vit-D binding proteins (DBP)
and 0.4% as free form
indirect PTH inhibition bu Vit D
- feedback (through plasma conc of Ca)
PTH secretion is regulated bu
ionized plasma Ca
The active form of Vit D and its classification
Calcitriol
classified as steroid hormone
Rapid Ca mobilization response to PTH
From Soluble form
besides calcitriol, calcityonin and PTH what other hormones affect Ca homeostasis
glucocorticoids
thyroid H
GH
EST and And
given Ca conc. is 10 mg/ dl
and pi is 4 mg/dl what are the %distributions of various forms
Ca: 50% ionized- 45% protein bound and 5% complexed with ions
Pi: 84% ionized (Free), 10% protein bound and 6% complexed with ions