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Flashcards in Renal Phys--> Ca2+ Deck (18):
1

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

2

How much Ca is found in bone? how much is left for extracellular?

about 99%
- leaves about 1% for extracellular space

3

What is the extracellular conc of calcium?

8-10mg/dL

4

How much Calcium is bound to albumin typically?

40%
- leaves about half left
- 4-5 mg/dL

5

How much calcium gets filtered per day then?

Depends on how much is bound and other things
5.7g-10.8 g/day
- based off of 180l/day

6

How much Ca2+ is excreted in the urine then?

about 200 mg/day

7

How much of calcium is bound to other stuff? what is that other stuff?

10%
- phosphate and citrate
- thus about 50% free calcium

8

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

9

What is the main form of absorption in the PCT for Ca?

Paracellular
only 15% being transcellular

10

what is the main form of absorption in the TAL for Ca?

Paracellular

11

What is unique about the TAL Calcium absorption?

Uses Claudins
- Calcium sensing receptor found on basolateral side of cell

12

What is the role of the calcium sensing receptor?

When calcium is NOT bound it upregulates Claudins

13

What the role of claudins in calcium absorption?

Protein that helps Ca get across the paracellular pathway!
- Upregulated when we are LACKING in calcium

14

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

15

How is Ca get absorped in the distal convuluted tubule?

Transcellular
- TRPV5

16

What is Calbindin?

Shuttle protein that moves Ca from Lumen side of cell to basolateral side of cell.

17

how does Ca leave the cell on the basolateral side?

1. ATP driven Ca channel
1. 3:1 Na:Ca anti-porter

18

What upregulates Calcium absorption and how?

PTH
- upregulates activity of TRPV5 as well as both channels for Ca extrusion (Calcium leaving the cell on basolateral side)