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Health.1 > Endocrine func of kidney > Flashcards

Endocrine func of kidney Flashcards

1
Q

3 endocrine functions of kidney?

A

renin prodn
EPO func and prodn
VitD activation and funcn - control of Ca and Phosphate

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2
Q

whats erythropoiesis?

what does it allow

A

RBC production

= O2 supply to organs and tissues

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3
Q

what does lack of erythrocytes (RBCs) ->?

A

anaemia

  • fatigue
  • reduced exercise tolerance
  • red brain funcn
  • inc risk of CVD
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4
Q

affect of hypoxia on RC prodn?

A

increases it

high altitude = hypoxia) -> inc red cell mass (haematocrit

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5
Q

When is EPO gene transcription increased?

A

low oxygen
low iron
low haematocrit

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6
Q

What is the main adult and foetal site of EPO production?

A

adult: cortical fibroblasts
foetal: liver

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7
Q

What detects low O2 levels?

A

hypoxia inducible transcription factors

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8
Q

What happens in the case of normal oxygen?

A

HIF-1a degraded

proline on HIF-1a is hydroxylated
it binds with Von Hippel Lindau
complex formed with E3 ubiquitin ligand complex
protein broken down into amino acids = proteasomal degradation

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9
Q

What happens in the case of low oxygen?

A

in hypoxia- hydroxylation is inhibited and HIF-1a is stabilised, forms complex w HIF-1b

HIF-1a forms a complex with HIF-1b
this forms a complex with AHNT
production of erythropoetin mRNA

(– hypoxia response elements -> gene transcription)

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10
Q

what happens to HIF1-alpha in case of

a) normal O2
b) hypoxia

A

a) degraded (binds to Von Hippel Lindau… E3 Ub ligase complex… protein -> free units_
b) hydroxn inhibited. HIF-1a stabilised, forms complex with HIF1-b…. -> nucleus, complex w AHNT (hypoxia responsive element) -> gene transcription activated

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11
Q

what is EPO gene trans controlled by?

A

cellular Fe and O2 levels

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12
Q

What type of receptor is EPO receptor and wheres it expressed?

A

homodimeric receptor on red cell rpecursors

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13
Q

What does signalling of the EPO receptor lead to?

A

less RBC apoptosis
more proliferation
more differentiation

alow redn, inc O2 carrying abilities

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14
Q

What’s the link between EPO and Ang II?

A

Ang II increases EPO production

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15
Q

Why is EPO considered a dangerous drug if abused?

A

increased risk of clots and hypertension

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16
Q

describe how/why Ang II increases EPO production in bone marrow

A

done to ↑ differentiation of stem cells in retic.
↑eryth production in bone marrow = ↑Hb levels = ↑O2 levels + carrying capacity –> kidneys ☺ so can produce EPO if sufficient O2

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17
Q

interaction between EPO and Ang II?

how about ACEi and ARB?

A

Ang II probably -> ↑ EPO prodn

  • ACEi and ARB reduce EPO prodn
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18
Q

whats EPO treatment associated with?

A

decr plasma volume

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19
Q

What are consequences of failure to produce EPO?

A

reduced production of erythrocytes and oxygen delivery to tissues
impaired quality of life = reduced exercies capacity
transfusion requirement- Fe overload, blood-bourne infection
risk of left ventricular hypertrophy
CVD risk in patients with CKs and anaemia vs those without

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20
Q

effect of EPO on endurance/ excersice capacity?

A

↑ haematocrit (eryth content of blood)
= ↑ exercise capacity (VO2 max)
= ↑ endurance

= drug of abuse

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21
Q

What are normal Hb levels for men and women?

A

men: 14-17.5gm/dL
women: 12.3-15.3gm/dL

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22
Q

4 things to monitor regarding EPO?

A

Hb target: 100-120g/L
BP (EPO induced hypotension)
thrombosis
anaemia teams

23
Q

EPO produced by cortical fibroblasts in response to? (2)

A

hypoxia

low iron

24
Q

EPO affect on erythrocyte prodn in bone marrow?

A

increases

… inc O2 delivery to tissue

25
Q

what system does EPO interact with?

A

Renin-angiotensin

26
Q

Why are calcium and phosphate serum concs tightly regulated?

A

as vital for:
muscle function
cardiac function
bone metabolism

27
Q

what 2 things is only Ca vital for?

A

Ca: nerve function and blood clotting

28
Q

what things is only Phosphate vital for?

A

multiple cellular funcs inc

  • energy metabolism
  • cell signalling
29
Q

whats body Ca and phosphate content the balance between?

A

gut absortpion and renal excretion

both widely distributed in tissues with a huge reservoir in bone- can release back into blood if needed

30
Q

2 key hormones involved in control of Ca and phosphate?

A

Vit D

parathyroid hormone

31
Q

organs involved in Ca and phosphate homeostasis?

A

gut: absorption

bone pool: for exchange

kidneys: excretion

32
Q

What is activated Vitamin D important in the regulation of?

A
  • serum calcium - uptake and reabsorption
  • serum phosphate
  • bone turnover - normal osteoclast and osteoblast activity
    induces calcium sensor expression on parathyroid glands
    supresses 1a hydroxylase and promotes 24 hydroxylase negative feedback
  • other
33
Q

How is Vitamin D activated?

A

sun - UV light turns it into cholecalciferol
25-hydroxylase turns it into 25(OH)D3
DBP turns it into 25(OH)2D3 via 1a-hydroxylase
then taken up from filtrate by PTEC

34
Q

where is Vitamin D activated?

A

in proximal tubule epithelial cells..

then active form transported back to blood

35
Q

where does rate limiting step happen?

A

in kidney proximal tubular epithelium:

25(OH)D3 –> 25(OH)2D3 via 1a-hydroxylase

36
Q

if have non func kidney, why will you not get active vit D3?

A

as rate limiting step happens inin kidney proximal tubular epithelium:
25(OH)D3 –> 25(OH)2D3 via 1a-hydroxylase

37
Q

What is 25(OH)2D3 (vitamin D3) converted into if theres too much?

A

inactivated…
24-hydroxylase turns it into calcitroic acid in cell (soluble and inactive)

transfer to nucleus to promote gene transcription

38
Q

How is gene transcription of vitamin D increased?

A

activated vitamin D binds to IDBP

activation of vitamin D receptor

increased gene transcription

39
Q

Role of Vit D?

A
  • promotes Ca and phosphate uptake form intestinal lumen
  • vital for osteoblast and osteoclast activity (bone turnover and remodelling)
  • increases Ca reabsorption form tubule
  • helps maintain normal serum Ca
  • induces Ca sensor expression on parathyroid glands (-ve feedback)
  • suppresses 1a-hydroxylase and promotes 24-hydroxylalse in kidney (-ve feedback)
40
Q

how does low Ca act as signal to increase serum Ca?

hint: PTH

A

caused by low Ca -> PTH released from parathyroid -> inc bone resorption (more released) -> inc serum Ca

41
Q

what does parathyroid affect?

A

releases PTH (works to inc Ca levels), affects:

  • kidney: 25vitD -> 1,25vitD -> inc intestinal Ca absorption in gut
  • bone: inc bone resorption
42
Q

what happens regarding PTH when serum levels of Ca successfully increased?

A

signal sent to parathyroid to stop making PTH

43
Q

What happens in the case of renal failure and low calcium regarding Vit D, Ca, PTH?

A

low Ca:

  • kidney: 25vitD -> 1,25vitD -> CANT DO!!
  • only bone: inc bone resorption -> inc serum Ca

therefore serum Ca lower

44
Q

consequence of constantly stim Parathyroid?

A

hyperparathyroidism
- parathyroid glands create too much PTH in the bloodstream

hyperphosphataemia
- abnormally high serum phosphate levels- from increased phosphate intake, decreased phosphate excretion, or a disorder that shifts intracellular phosphate to extracellular space

45
Q

What is ectopic calcification?

A

inappropriate biomineralization occurring in soft tissues.

Ectopic calcifications are typically composed of calcium phosphate salts, including hydroxyapatite, but can also consist of calcium oxalates and octacalcium phosphate as seen in kidney stones.

= severe bone pain on moving
long term CVD - harm
not always kidney disease- calcification of vessels

(see veins on xray)

46
Q

2 types of (ectopic) calcification

A 
arterial (see veins on xray)
soft tissue (severe bone pain)
47
Q

What treatments prevent bone disease and ectopic calcification?

A
  • 1a-hydroxylated vitD replacement
  • phosphate restriction
  • phosphate binders
  • calcimimetics

if all fails- parathyroidectomy

48
Q

what do calcimimetics do?

used in what disease state?

A

work by decreasing the levels of PTH (responsible for maintaining proper levels of both calcium and phosphorus in the body).
The right amount of these substances in the body helps to prevent progressive bone disease.

(good for parathyroidism)

49
Q

phosphate binders: Ca/ renal Ca based depending on?

A

serum Ca with/ before food every time!

take w lots of phosphate meds

50
Q

vit D/ PTH

what to monitor?
how to treat

A

Ca, phosphate, PTH

treat w varying doses:

  • alfacalcidol: inc Ca uptake in gut (bad if have inc Ca)
  • cinacalcet
  • Ca (supplement)

phosphate control = dialy battle. encourage, advice

51
Q

when are phosphate binders given? (for phosphate control- preventing bind disease and ectopic calcification)

A

before food everytime!!
thick chalky tablets
unpleasant

52
Q

what is vitD?

A

steroid hormone
- rate limiting step in kidney

(vit D precursors intake/meds need func liver and kidney to actuate)

53
Q

whats Vit D intimately involved with?

A

Ca and phosphate homeostasis

interactions between
Vit D and PTH

exchange of ions between gut, blood, kidneys, bones

54
Q

how do kidnyes maintain bone density?

A

create enz to activate partially vit D and inc blood Ca.

and not constantly release Ca and phosphate from bone

Health.1 (12 decks)

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