Lecture 8: Calcium and Phosphate Regulation Flashcards
What is the normal serum range of calcium?
2.2-2.6mM
Why is calcium important?
1) membrane stability
2) neuronal transmission
3) bone structure
4) blood coagulation
5) muscle function
6) hormone secretion
What is phosphate used for?
cellular energy metabolism (ATP)
Hypoventiliation leads to ________________ which results in muscle weakness, renal dysfunction, hypoexcitability
hypercalcemia
Hyperventilation leads to _______________ which results in hyperexcitability
hypocalcemia
True or False: there is 10 fold more P than Ca in soft tissue
True
BUT there is more calcium in serum
Calcium travels in the blood bound to what protein?
albumin (45% bound, 50% ionized)
therefore, albumin levels are a good indicator of free calcium availability
What are the 3 regulators of calcium
1) Parathyroid (PTH)
2) Vitamin D (Calcitriol)
3) Calcitonin
What contributes most to the rapidly exchangeable pool of calcium in the body?
constant turnover of bone
What and where are parathyroid glands?
paired glands (4 total) at the posterior borders on lateral lobes of thyroid glands
What 2 cells are found in parathyroid glands?
1) Chief/Principal —–> make PTH
2) Oxyphil —–> no known function
What is the half life of the entire 84 amino acid PTH?
4 minutes!
Which portion of the PTH molecule binds to the receptor?
N-terminal fragment
What is PTHrP?
parathyroid hormone related peptide
- mimics PTH in bone and kidney (normally at LOW conc, not regulator of plasma Ca)
- produced by tumors resulting in hypercalcemia
What is the primary receptor of PTH?
PTH 1R (on osteoblasts and kidney)
- binds N terminal 1-34 fragment, 1-84, PTHrP
What kind of receptor is PTH 1R?
GPCR
What does PTH 2R do?
binds 1-34, not sure what else
The net effect of PTH is to __________ plasma Ca++ and __________ plasma P
increase calcium
decrease phosphate
Where is one of if not the largest PTH target?
bone (99% of Ca content is in bone)
True or false: osteoclasts have PTH receptors
false – all effects of PTH on bone happen kind of indirectly
KEY: PTH stimulation of osteoclasts is INDIRECT
What kind of cells make up most of the bone matrix?
osteocytes (terminally differentiated osteoblasts)