Renal tubular disorders

Question 1

What is renal blood flow per min?
What is the renal plasma flow?
What is the glomerular filtration rate?
what is the urine flow rate?

Answer 1

120ml/min
-

Question 2

What happens in the proximal tubule?

Answer 2

Active reabsorption of multiple solutes
Metabolically active cells - lots of mitochondria
Sodium gradient generated by Na/K ATPases
Vulnerable o hypoxia, VERY to toxicity

Question 3

Which solutes are reabsorbed in the proximal tubules?

Question 4

How does renal glycosuria show function of the proximal tubule?

Answer 4

Shows it reabsorbs glucose
defect in sodium glucose transporter 2 (SGLT2) means glucose isn’t reabsorbed
Excess glucose found in urine

Question 5

How does aminoaciduria e.g.cystinuria show function of the proximal tubule?

Answer 5

Shows it reabsorbs amino acids such as cystine
Failure of cystine reabsorption - crystallises in urine and forms stones (cystine stones)
Treat with high fluid intake (lower conc, high urine flow), alkalinise urine to increase solubility of cystine, drugs, remove stones physically

Question 6

How does hypophosphataemic rickets show the function of the proximal tubule?

Answer 6

Shows it absorbs phosphate
commonest form is XLH, genetic defect, can;t reabsorb phosphate
Treat with phosphate replacement

Question 7

Which proteins are involved (main) in bicarbonate reabsorption in the proximal tubules of the kidney?

Answer 7

Carbonic anhydrase - H2CO3 converted to its subsequent ions
Sodium hydrogen antiporter- absorb Na+, release H+ into tubular lumen

Question 8

What occurs in bicarbonate reabsorption?

Question 9

How does proximal(type 2) renal tubular acidosis show function of the proximal tubule?

Answer 9

Shows it recycles HCO3- ions

Defect in Na/H antiporter, failure to reabsorb
Presents acidosis, impaired growth
Supplement bicarbonate to treat

Question 10

How does rfanconi syndrome show function of the proximal tubule?

Answer 10

Generalised proximal tubular dysfunction
Possibly due to failure to extablish sodium gradient by Na/K ATPase
Causes - genetic, myeloma, lead poisoning, cisplatin
Clinical presentation are ALL the other disorders together

Question 11

What is the function of the loop of Henle?

Answer 11

Generates medullary concentration gradient
Active Na reabsorption in thick ascending limb

Question 12

What is the function of the thick ascending limb in the loop of Henle?

Answer 12

Reabsorb …
Recycle …

Question 13

What proteins are involved in thick ascending limb function (loop of Henle)?

Question 14

What is the function of the distal tubule and collecting duct?

Answer 14

Distal tubule and cortical collecting duct allow ‘fine-tuning’ of sodium reabsorption, potassium and acid-base balance

Collecting duct mediates water reabsorption and urine concentration

Question 15

what detects the drop in blood pressure? What do they produce?

Answer 15

JGA in the kidney (juxtaglomerular…) - renin
Baroreceptors in the aorta - increased sympathetic output
Atrial stretch receptors in the heart - reduced ANP synthesis

Question 16

control of blood pressure renin

Question 17

What proteins are involved in the actions of aldosterone?

Question 18

How does aldosterone act on the kidney?

Answer 18

Steroid hormone, acts on the nucleus - transcription - increases expression of ENaC, Na/K ATPase
So affects absorption
Allows entry of cortisol??

Question 19

How does excessive aldosterone activity affect the kidneys?

Answer 19

Produces sodium retention, hypertension, hypokalaemic alkalosis
Can be primary or secondary, some disorders present with similar symptoms (AME)

Question 20

What is the mineralocorticoid receptor FOR?

Answer 20

Can it be activated by both aldosterone AND cortisol? yes
normally cortisol entry to renal tubular cells prevented by 11-beta hydroxysteroid dehydrogenase
Part of the RAAS system, aldosterone activates it other stuff can, e.g. cortisol when its not destroyed by the brush border

Question 21

What part of the kidney does nephrogenic diabetes insipidus show there’s an issue with?

Answer 21

Collecting duct
Defect in vasopressin V2 receptor or aquaporin 2 water channel
Failure of water reabsorption in collecting duct, inability to concentrate urine
Causes sodium retention - body trying to maintain volume - losing water but retaining sodium