kidney

Question 1

Physiological roles of the kidney and disease which treatments target the kidney

Answer 1

Acid-base balance through modulating bicarbonate levels

reabsorbance of fluid and electrolyte balance (and consequently blood pressure)

excretion of waste products such as urea, uric acid, and creatinine.

Hypertension, cardiovascular diseases, and diabetes are diseases that can be treated by targeting the kidneys

Question 2

Classes of diuretics and where in the nephron they act

Answer 2

In consequtive order of where they act in the nephron:

Carbonic anhydrase inhibitors (proximal convoluted tubule)

Osmotic diuretics (proximal convoluted tubule and loop of henle)

Loop diuretics (loop of hence)

Thiazides (distal convoluted tubule)

Aldosterone antagonists (collecting duct)

ADH (vasopressin) antagonists (collecting duct)

Question 3

Osmotic diuretics mechanism

Answer 3

e.g., mannitol

They increase the osmolarity of the tubular fluid (the urine), reducing the passive reabsorption of water.

Used for cerebral oedema

Question 4

Loop diuretics mechanism

Answer 4

e.g., furosemide, bumetanide

They block the Na+/2Cl-/K+ symporter that mediate the reabsorption of these ions from the urine.

They also lead to increased Ca2+ loss.

May cause hypokalaemia due to increased efflux of K+ ions due to higher activity of the Na+/K+ pump.

Used in left ventricular failure (due to ventilatory effects), pulmonary oedema, and renal failure.

Question 5

Thiazide mechanism

Answer 5

e.g., bendrofumethiazide

Inhibits the Na+/Cl- symporter, increasing the amount of ions in the urine. Decreases the gradient for water reabsorption.

This increases the activity of the Na+/K+ pump, which can lead to hypokalaemia.

Question 6

Examples and mechanisms of potassium sparing diuretics

Answer 6

Na+ channel blockers, e.g., amiloride, triamterene, which blocks the luminal Na+ channel (reabsorption) in the distal convoluting tubule and the collecting duct

Aldosterone receptor antagonists, e.g., spironolactone, reduces the expression of Na+ pumps and channels. Leads to less reabsorption of sodium: higher excretion.

Question 7

Types of dialysis

Answer 7

Hemodialysis, and peritoneal dialysis

Hemodialysis takes the blood and filters it.

Peritoneal dialysis puts the dialysis solution into the abdominal cavity of the individual. More rare.

Question 8

Drugs that target urinary incontinence and retention

Answer 8

Oxybutynin, tolterodine and darifenacin are M3 antagonists that reduce the SM tone in the bladder - treat urinary retention

Duloxetine a SNRI

Amtiriptaline a TCA

and desmopressin, a synthetic analogue of vasopressin: decreases urine formation in kidney