Flashcards in Renal Phys--> Ca2+ Deck (18):
How much Calcium does one typically consume per day? how much of this is excreted in feces?
about 1 gram
about 80% excreted in feces (0.8g)
- means about 0.2g/day is absorbed
How much Ca is found in bone? how much is left for extracellular?
- leaves about 1% for extracellular space
What is the extracellular conc of calcium?
How much Calcium is bound to albumin typically?
- leaves about half left
- 4-5 mg/dL
How much calcium gets filtered per day then?
Depends on how much is bound and other things
- based off of 180l/day
How much Ca2+ is excreted in the urine then?
about 200 mg/day
How much of calcium is bound to other stuff? what is that other stuff?
- phosphate and citrate
- thus about 50% free calcium
What is the segmental absorption percentage of Ca in the kidney?
60-60% in PCT
20 in TAL
10% in DCT
0-5% in Collecting duct
Very similar to Na
What is the main form of absorption in the PCT for Ca?
only 15% being transcellular
what is the main form of absorption in the TAL for Ca?
What is unique about the TAL Calcium absorption?
- Calcium sensing receptor found on basolateral side of cell
What is the role of the calcium sensing receptor?
When calcium is NOT bound it upregulates Claudins
What the role of claudins in calcium absorption?
Protein that helps Ca get across the paracellular pathway!
- Upregulated when we are LACKING in calcium
What is also unique about the calcium sensing receptor in terms of Na?
When loads of Ca is bound to the calcium sensing receptor it can DOWNREGULATE the NKCC channel. Thus, creating less of a positive charge in the urine lumen and decreases paracellular transport of Ca
How is Ca get absorped in the distal convuluted tubule?
What is Calbindin?
Shuttle protein that moves Ca from Lumen side of cell to basolateral side of cell.
how does Ca leave the cell on the basolateral side?
1. ATP driven Ca channel
1. 3:1 Na:Ca anti-porter