Kidney As Endocrine Glands

Question 1

What is the main endocrine protein released from the kidneys

Answer 1

Erythropoietin

Question 2

Where is EPO synthesised

Answer 2

By the mesangial cells and renal tubular cells

Question 3

What is EPO released in response to

Answer 3

Hypoxia which is detected in the kidney in the renal medulla when perfused with blood

Question 4

What does hypoxia induce the release of in the mesangial and renal tubular cells and what does it do

Answer 4

Prostaglandin

Stimulates EPO synthesis and secretion

Question 5

What is EPO synthesis and secretion mediated by

Answer 5

HIF

Hypoxia inducible transcription factor which is activated in the mesangial and tubular cells

Question 6

What else controls EPO release

Answer 6

Autonomic NS control mediated by sympathetic noradrenaline binding to beta adrenoreceptors in the kidney

Question 7

What does EPO do when secreted

Answer 7

Goes to the bone marrow where it acts on the EPO receptors to increase the production of pro-erythroblasts

Question 8

What happens to EPO production in renal failure

Answer 8

It decreases and leads to anaemia

Question 9

What kidney disease is usually an exception to the decreased EPO

Answer 9

Polycystic kidney disease
As sufficient mesangium remains to be able to synthesise enough EPO
However, if the GFR falls the incidence of anaemia will increase

Question 10

What is the treatment for anaemia in renal failure

Answer 10

EPO analogues

Question 11

Where is EPO analogues produced from

Answer 11

Cell culture

Question 12

Commonest EPO analogue and how is it different

Answer 12

EPO alpha and is mutated to become more glycosylated

Question 13

EPO analogues use elsewhere

Answer 13

Sport to increase endurance by more EPO

Increasing haematocrit levels

Question 14

Problem with its use for people with normal blood cell levels anyway

Answer 14

Increase haematocrit too much which can lead to increased risk of thrombosis

Question 15

Vitamin d conversion in the liver and kidney

Answer 15

Vitamin d taken in via food and at the skin via sun light
Converted in the liver to 25-hydroxycholecalciferol
Kidney to 1,25-dihydroxycholecalciferol
In the kidney the enzyme 1alpha hydroxylase is responsible for this
Production of 1,25-vd stimulated by PTH and inhibited by calcitonin
Increase calcium and phosphate absorption in gut and retention in kidneys

Question 16

What does the kidney secrete is response to low arteriolar BP, sympathetic stimulation, or lowered Na+ in the distal tube

Answer 16

Renin from the granular cells of the juxtaglomerular apparatus