Urology & renal - Renal regulation of water and acid-base balance

Question 1

What are the unregulated methods of water loss?

Answer 1

• Sweat
• Feces
• Vomit
• Water evaporation from respiratory lining and skin

Question 2

What is the regulated method of water control?

Answer 2

Renal regulation - urine production

Question 3

What is the first effect when there is a high water intake?

Answer 3

Extra cellular fluid volume rises

Question 4

What percentage of water is absorbed in the proximal convoluted tubule?

Answer 4

67%

Question 5

What are the 2 urea transporters in the collecting duct?

Answer 5

UT-A1: Apical side

UT-A3: Basolateral side

Question 6

What can absorb urea after it has been pumped into the interstitium and through which urea transporters?

Answer 6

The vasa recta - UT-B1
or
The loop of henle - UT-A2

Question 7

What is the act of vasopressin on urea transporters?

Answer 7

It increases the numbers of UT-A1 & UT-A3

Question 8

Where is vasopressin produced and stored?

Answer 8

Produced:
The neurons in the supraoptic & paraventricular nuclei in the hypothalamus

Stored:
The posterior pituitary

Question 9

What factors influence ADH production and release?

Answer 9

Stimulatory:

• Increased plasma osmolarity
• Decreased blood pressure (hypovolemia)
• Nausea
• Angiotensin II
• Nicotine

Inhibitory:

• Decreased plasma osmolarity
• Increased blood pressure (hypervolemia)
• Ethanol
• Atrial natriuretic peptide

Question 10

What is the mechanism of action of ADH?

Answer 10

• ADH binds to V2 receptors on the basolateral cell membrane
• THis activates G-protein which then activates Adenylate cyclase
• This converts ATP to cAMP
• This then binds with Potein kinase A to release more Aquaporin 2 channels
• These bind to the apical cell membrane and increase the amount of water going from the collecting duct to the blood

Question 11

How is bicarbonate produced and reabsorbed in the kidneys?

Answer 11

• CO2 enters the proximal convoluted tubule by diffusion
• This reacts with H2O with the help of carbonic anhydrase to produce H+ and HCO3-
• H+ is absorbed by the Na+-H+ anitporter or the V-ATPase pump into the tubular fluid
• HCO3- is reabsorbed by the Na+ - HCO3- symporter, into the blood

Question 12

What are the function of the alpha and beta inctercalated cells in the distal convoluted tubule and the collecting duct?

Answer 12

Alpha - HCO3- reabsorption and H+ secretion

Beta - HCO3 - secretiona and H+ reabsorption

Question 13

How is bicarbonate produced in the kidneys?

Answer 13

In the proximal convoluted tubule (amoniogenesis):

• Glutamine produced 2 ammonia and 1 glutamate ion
• The glutamate ion then produces 2 bicarbonate ions which are absorbed into the blood