Flashcards in hormones in Ca metabolism Deck (31)
where is prepro PTH synthesized?
in ribosomes of parathyroid chief cell
what is cleaved before the preproPTH moves from the ribosome to the ER?
cleaved at 25 aa in N terminus
preproPTH is converted into ProPTH when?
After removal of the N-terminal sequence of 25 amino acids
proPTH is converted into PTH when?
when a hexapeptide from the N terminal is cleaved by trypsin like enzymes in golgi
where is PTH stored?
golgi complex of parathyroid chief cell
negative feedback on PTH comes from? (2)
2. Vitamin D
what detects changes in the plasma calcium?
Ca2+-sensing receptor (CaR) on parathyroid
when Ca binds CaR, trigger signal via ______, which produces____
phospholipase C; leukotrienes
what is responsible for degrading already synthesized PTH, and decreasing the release of PTH?
what has the ability to suppress the txn of mRNA of PTH?
in hypocalcemia, is Ca sensor receptor active or relaxed?
what triggers PTH synthesis and secretion?
relaxed Ca sensor receptor
where is the CaR present? (3)
1. parathyroid chief cells
2. thyroid C cells
3. kidney tubules
binding of PTH to PTHR1 leads to what pathway (2)
1. AC Pathway
2. PLC Pathway
effect of PTH in kidney?
stimulates insertion and opening of Ca channel, and Ca reabsorption
what does Vit D activate in kidney?
Ca ATPase, and controls calbindin D28K
PTH permits opening of Ca channel on the ____membrane of the kidney _____
apical; distal tubules
what is calbindin D28K
vitamin D–dependent calcium-binding protein in renal tubule
what direction does calbindin permit flow of Ca in the distal tubule?
binding of PTH to osteoblast leads to expression of ____
binding of RANKL to RANK on____, leads to formation of _____
osteoclast precursor; mature osteoclast
what can inhibit the binding of RANKL to RANK and prevent bone resoprtion?
PTH _______ osteoprotegerin
what is the plant version of Vit D?
Vit D2 (ergocalciferol)
what is the animal version of Vit D?
Vit D3 (cholecalciferol)
what enzyme directly leads to synthesis of active Vit D?
target organs of Vit D
4. parathyroid glands
role of calcitrol on renal Ca absorption?
calcitriol _____Ca ATPase and ____calbindin D28K
calcitonin _____bone resorption, ____urinary Ca excretion