Endo control of Ca2+/PO4 metabolism (lec 24)

Question 1

Ca2+ critical for?

Answer 1

nm fxn
secretion
hemostatis/clotting
enz fxn
teeth/bones

Question 2

PO4 critical for?

Answer 2

cell energy metabolism
enz A and deA
bones/teeth

Question 3

Humoral (blood elements) secretions are activated by?

Answer 3

[substance] in blood

Question 4

PTH synthesis?

Answer 4

in chief cells -> preproPTH ->
secretory vesicles ->
Ca2+ receptors stim or inhibit synth/release of PTH

Question 5

Ca2+ inhibits PTH how?

Answer 5

Ca2+ binds G-prot -> activates PLC -> IP3/DAG -> internal Ca2+ release -> inhibit PTH syth/release

Question 6

Main effects of PTH?

Answer 6

1) bone resorption (pull Ca2+ and PO4 into ECF)

2) promote Ca2+ reab at kidney/inhibit PO4 reab at kidney

Question 7

Role of PO4 released from bone?

Answer 7

binds Ca2+ in ECF -> ↓ free Ca2+

Question 8

PTH action on PCT in kidney?

Answer 8

Binds Gs -> cAMP -> blocks Na+/PO4 cotrans from lumen into cell

Net effect on plasma: ↓ [PO4], ↑ [free Ca2+]

Question 9

Vit D activated by what enz?

Active Vit D?

Inactive Vit D?

Answer 9

1⍺-hydroxylase (neg feedback of vit D inhibits)

1,25-(OH)2-cholecalciferol

24,25-(OH)2-cholecalciferol

Question 10

Effects of PTH, Ca2+, PO4 on 1⍺-hydroxylase?

Answer 10

1⍺-hydroxylase stimulated by:
↑ PTH
↓ Ca2+/PO4

Question 11

Active Vit D effect on intestines?

Answer 11

Stim all steps of transcellular Ca2+ in duodenum: stim caldindin syth -> ↑ absorption of Ca2+/PO4

Question 12

Ca2+ absorption in intestines? (2)

Answer 12

1) Vit D stimulated transcellular absorp

2) Passive, paracellular absorption

Question 13

Vit D effect on kidney?

On bone?

Answer 13

Ca2+ reab from DCT

Directly mobilize Ca2+ from bone (resorption),
Indirectly ↑ bone mineralization via ↑ Ca2+

Question 14

PTH effects on kidney? (3)

Answer 14

1) ↑ Ca2+ reab -> ↑ plasma [Ca2+]
2) ↓ PO4 reab
3) Activation of Vit D -> ↑ Ca2+ reab

Question 15

PTH effect on bone?

Answer 15

↑ bone resorption -> ↑ plasma [Ca2+]

Question 16

PTH effect on intestines?

Answer 16

Activate Vit D -> ↑ Ca2+ reab

Question 17

Net ↑ in plasma [Ca2+] affects PTH how?

Answer 17

↓ PTH release

Question 18

Calcitonin is?

Produced where?

Answer 18

PTH antagonist

Parafollicular C cells of throid

Question 19

Calcitonin effects on bone?

Answer 19

↑ plasma [Ca2+] stimulates calcitonin release ->

inhibit bone resorption -> ↓ plasma [Ca2+]/[PO4]

Question 20

Calcitonin effects on kidney?

Answer 20

stim excretion of Ca2+/PO4 in urine -> ↓ plasma [Ca2+]/[PO4]

Question 21

Calcitonin effect on intestines?

Answer 21

none

Question 22

Rickets is?

Results in?

Answer 22

Vit D deficiency in kids

insufficient bone growth
hypoCa2+
↑ PTH

Question 23

Osteomalacia is?

Results in?

Answer 23

Vit D deficiency in adults

soft bones
hypoCa2+ tetany
↑ PTH

Question 24

Hyperparathyroidsim (U) caused by?

Results in?

Answer 24

PTH adenoma -> ↑ PTH -> ↑ Ca2+

Stone, bones, abd groans, psychic moans, fatigue overtones

Question 25

HypoPTHism (U) caused by?

Results in?

Answer 25

removal of parathy during thyroidectomy

hypoCa2+
hyperPO4
tetany
convulsions

Question 26

Pseudohypoparathyroidism is?

Results in?

Answer 26

non-fxning G-protein receptors

↑ PTH
hypoCa2+
hyperPO4
growth abnormalities