Diuretics Flashcards
The proximal tubule is permeable to what?
Water and sodium
Which side exchanges sodium for potassium and via what?
Basal (blood) end, via sodium potassium ATPase
Which pressure from the blood acts to reabsorb water?
Oncotic pressure
How do glucose and amino acids get reabsorbed and where?
Coupled to sodium transport, in PCT
How does bicarbonate get reabsorbed in the PCT?
Carbonic anhydrase converts hydrogen ions and HCO3- to CO2 and water in the lumen. These are taken into the cell. The same enzyme does the reverse reaction. The bicarbonate produced is coupled with sodium and is reabsorbed into the blood.
What moves from the blood to the lumen in the PCT?
Exogenous agents
Which limb is permeable to water?
Descending limb only
Which transporter exists on the apical side of the ascending limb?
Sodium chloride potassium triple transporter
Which main ions are reabsorbed in the ascending limb of the loop of Henle?
Sodium and chloride
What is the countercurrent effect?
Concentrated interstitium in comparison to loop of Henle, as sodium can move out of ascending limb, but not the descending limb, so the interstitium becomes more concentrated in comparison to the tubule
Which transporter exists in the early distal tubule?
Sodium chloride transporter
Which part of the kidney is aldosterone sensitive?
Late distal tubule
Describe the water movement via distal tubule.
Impermeable to water in early distal tubule due to tight junctions between cells and lack of transport proteins.
Unless there aquaporins in the later distal tubule it can’t move through.
What is the effect of the countercurrent effect?
Enables osmotic gradient for reabsorption of water in the late distal tubule and collecting duct
Explain how and where osmotic diuretics work. Give an example.
Mannitol - increases osmolality of tubular fluid therefore decreases concentration gradient between tubule and interstitium, therefore water reabsorption decreased
Which transporter is blocked by loop diuretics and where? What is the effect of this?
Triple transporter of ascending limb. Interferes with counter current effect.
What is a side effect of loop diuretics and why?
Normally some potassium is recycled back to the lumen, which drives paracellular movement of calcium and magnesium. Loss of this means these ions are lost.
(Decreases positive lumen potential)
Why is potassium lost due to loop diuretics?
Increased delivery of sodium to later parts of the tubule means that the body tries to reabsorb it in exchange for potassium.
Which transporters are inhibited by thiazide diuretics and where does this happen?
Sodium chloride transporter at distal convoluted tubule
What three side effects result from thiazide diuretics?
Hypokalemia (in exchange for sodium at later parts of the tubule)
Magnesium loss
Calcium reabsorption
Low tubular sodium normally stimulates renin. Yet renin secretion increases as a result of diuretics. Why?
Reduced renal perfusion pressure stimulates the macula densa cell.
Which diuretic activates the renin secretion quite badly?
Loop diuretics, due to blockage of triple transporter which also signals to macula densa cell?
What is given to counteract renin production with diuretics?
ACE Inhibitors
Name two classes of potassium sparing diuretics
Aldosterone receptor antagonists
Inhibitors of aldosterone sensitive sodium channels