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Flashcards in hormones in Ca metabolism Deck (31)
1

where is prepro PTH synthesized?

in ribosomes of parathyroid chief cell

2

what is cleaved before the preproPTH moves from the ribosome to the ER?

cleaved at 25 aa in N terminus

3

preproPTH is converted into ProPTH when?

After removal of the N-terminal sequence of 25 amino acids

4

proPTH is converted into PTH when?

when a hexapeptide from the N terminal is cleaved by trypsin like enzymes in golgi

5

where is PTH stored?

golgi complex of parathyroid chief cell

6

negative feedback on PTH comes from? (2)

1. Ca
2. Vitamin D

7

what detects changes in the plasma calcium?

Ca2+-sensing receptor (CaR) on parathyroid

8

when Ca binds CaR, trigger signal via ______, which produces____

phospholipase C; leukotrienes

9

what is responsible for degrading already synthesized PTH, and decreasing the release of PTH?

leukotrienes

10

what has the ability to suppress the txn of mRNA of PTH?

vitamin D

11

in hypocalcemia, is Ca sensor receptor active or relaxed?

relaxed

12

what triggers PTH synthesis and secretion?

relaxed Ca sensor receptor

13

where is the CaR present? (3)

1. parathyroid chief cells
2. thyroid C cells
3. kidney tubules

14

binding of PTH to PTHR1 leads to what pathway (2)

1. AC Pathway
2. PLC Pathway

15

effect of PTH in kidney?

stimulates insertion and opening of Ca channel, and Ca reabsorption

16

what does Vit D activate in kidney?

Ca ATPase, and controls calbindin D28K

17

PTH permits opening of Ca channel on the ____membrane of the kidney _____

apical; distal tubules

18

what is calbindin D28K

vitamin D–dependent calcium-binding protein in renal tubule

19

what direction does calbindin permit flow of Ca in the distal tubule?

basolateral-->apical

20

binding of PTH to osteoblast leads to expression of ____

RANKL

21

binding of RANKL to RANK on____, leads to formation of _____

osteoclast precursor; mature osteoclast

22

what can inhibit the binding of RANKL to RANK and prevent bone resoprtion?

osteoprotegerin

23

PTH _______ osteoprotegerin

inhibits

24

what is the plant version of Vit D?

Vit D2 (ergocalciferol)

25

what is the animal version of Vit D?

Vit D3 (cholecalciferol)

26

what enzyme directly leads to synthesis of active Vit D?

1-alpha hydroxylase

27

target organs of Vit D

1. intestines
2. kidney
3. bone
4. parathyroid glands

28

role of calcitrol on renal Ca absorption?

stimulates

29

calcitriol _____Ca ATPase and ____calbindin D28K

activates; controls

30

calcitonin _____bone resorption, ____urinary Ca excretion

inhibits; increases

31

what can calcitonin be used to tx?

1. osteoporosis
2. prevent hypercalcemia in malignancies