hormones in Ca metabolism

Question 1

where is prepro PTH synthesized?

Answer 1

in ribosomes of parathyroid chief cell

Question 2

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

Answer 2

cleaved at 25 aa in N terminus

Question 3

preproPTH is converted into ProPTH when?

Answer 3

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

Question 4

proPTH is converted into PTH when?

Answer 4

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

Question 5

where is PTH stored?

Answer 5

golgi complex of parathyroid chief cell

Question 6

negative feedback on PTH comes from? (2)

Answer 6

1. Ca

2. Vitamin D

Question 7

what detects changes in the plasma calcium?

Answer 7

Ca2+-sensing receptor (CaR) on parathyroid

Question 8

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

Answer 8

phospholipase C; leukotrienes

Question 9

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

Answer 9

leukotrienes

Question 10

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

Answer 10

vitamin D

Question 11

in hypocalcemia, is Ca sensor receptor active or relaxed?

Answer 11

relaxed

Question 12

what triggers PTH synthesis and secretion?

Answer 12

relaxed Ca sensor receptor

Question 13

where is the CaR present? (3)

Answer 13

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

Question 14

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

Answer 14

1. AC Pathway

2. PLC Pathway

Question 15

effect of PTH in kidney?

Answer 15

stimulates insertion and opening of Ca channel, and Ca reabsorption

Question 16

what does Vit D activate in kidney?

Answer 16

Ca ATPase, and controls calbindin D28K

Question 17

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

Answer 17

apical; distal tubules

Question 18

what is calbindin D28K

Answer 18

vitamin D–dependent calcium-binding protein in renal tubule

Question 19

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

Answer 19

basolateral–>apical

Question 20

binding of PTH to osteoblast leads to expression of ____

Answer 20

RANKL

Question 21

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

Answer 21

osteoclast precursor; mature osteoclast

Question 22

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

Answer 22

osteoprotegerin

Question 23

PTH _______ osteoprotegerin

Answer 23

inhibits

Question 24

what is the plant version of Vit D?

Answer 24

Vit D2 (ergocalciferol)

Question 25

what is the animal version of Vit D?

Answer 25

Vit D3 (cholecalciferol)

Question 26

what enzyme directly leads to synthesis of active Vit D?

Answer 26

1-alpha hydroxylase

Question 27

target organs of Vit D

Answer 27

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

Question 28

role of calcitrol on renal Ca absorption?

Answer 28

stimulates

Question 29

calcitriol _____Ca ATPase and ____calbindin D28K

Answer 29

activates; controls

Question 30

calcitonin _____bone resorption, ____urinary Ca excretion

Answer 30

inhibits; increases

Question 31

what can calcitonin be used to tx?

Answer 31

1. osteoporosis

2. prevent hypercalcemia in malignancies