GS Kidney clearance and kidney hormones

Question 1

1. List the causes of release of erythropoietin by the kidneys.

Answer 1

High altitudes
Haemorrhage
Red blood cell destruction
Increased tissue oxygen demands

The ability of RBCs to carry O2 determines the release of erythropoietin

Question 2

2. List the functions of erythropoietin.

Answer 2

Sustains red blood cell production

Stimulates bone marrow cell that are committed to becoming red blood cells.

Question 3

3. Describe how chronic renal failure affects the release of erythropoietin and what the consequence of this is.

Answer 3

As chronic renal failure progresses, the scarring that occurs leads to a decrease in functioning cells and a drop in the release of erythropoietin.
As a consequence, there is a reduced capacity of the blood to carry oxygen and the patient may present with lethargy as a result of anaemia.

Question 4

4. Describe how low levels of erythropoietin are treated in chronic renal failure.

Answer 4

Synthetic erythropoietin is now used in therapy to counter these effects.

Question 5

5. List the main actions of calcitriol (1,25-dihydroxycholecalciferol).

Answer 5

1. Stimulate the absorption of ingested Ca by increasing expression of Ca channels used to transport Ca across the cell membrane at the intestinal mucosa.
2. Increases phosphate absorption
3. Calcification of bone matrix by stimulation of osteoblasts and osteoclasts, facilitating the remodelling of bone

Question 6

6. Describe the effects of chronic renal failure on calcitriol production.

Answer 6

In renal failure, 25-hydroxycholecalciferol is not converted to 1,25-dihydroxycholecalciferol.
The kidneys add a hydroxyl group in this conversion

Question 7

7. Describe the effects of chronic renal failure on bone.

Answer 7

Leads to osteomalacia (softening of the bones) and osteoporosis (loss of bone tissue leading to brittle bones)