Kidney function & Diuretics Flashcards
(22 cards)
What is filtered from the blood at the Bowmans capsule via ultrafiltration
Salts, glucose, most small molecules
What 6 things are actively pumped back into the plasma at the proximal convoluted tubule
Water Sodium Potassium Bicarbonate Phosphate Glucose
How are glucose and sodium pumped back into plasma at the PCT
Using sodium / glucose co transporters e.g. SGLT2
What enzyme is responsible for producing bicarbonate (HCO3-) into the plasma, and excreting H+ into the urine at the PCT
Carbonic anhydrase
How much Na+ and water is reabsorbed at the PCT
65% of both
What is the basic 2 stage process of water and electrolyte reabsorbtion the occurs in the Loop of Henle “counter-current mechanism”
- Na+, K+ and Cl- actively pumped out of ascending limb into IS fluid
- Water drawn through osmosis (through aquaporins) into IS fluid by high conc of salts. Water quickly passes into vasa recta blood vessels and plasma. This draws salts in from IS fluid via osmosis.
What percentage of water and Na+ is reabsorbed at the LOH
20% H2O
25% Na+
What 2 ions are exchanged at the Distal convoluted tubule to maintain salt balance
Na reabsorbed into plasma, in exchange for K+ excreted in urine.
What is the kidney natural response to detecting hyperkalaemia
Renin is produced - increases Na+ reabsorption to plasma, - increases K+ extretion in urine.
PTH acts on the DCT to increase the reabsorption of what?
Ca++ - DCT is the main site of reabsorption in the kidney.
What is the basic process of responding to dehydration involving the hypothalamus, pituitary and kidney collecting duct
- Plasma increase in osmolality detected at Hypothalamus.
- Stimulates “thirst” sensation and production of ADH (vasopressin) from post. pituitary.
- ADH acts to open aquaporins at collecting duct - increases H2O reabsorption into plasma, therefore decr. urine production.
Where is the site of action of mannitol - how does it act as a diuretic
PCT - purely osmotic effect, draws H2O into tubule through increase osmotic pressure (think mannitol - similar to mannose - sugar - big molecule)
Mannitol draws water from cells into plasma / IS fluid, what other conditions / pathology can be treated with it?
For reducing intracranial / intra ocular pressure
Also in haemolysis and rhabdomylosis (why?)
Give 2 examples of loop diurectics (act on LOH)
Furosemide / Bumetonide
- How do loop diuretics work
- How does this relate to their side effects
- Random other SE of loop diuretics
- Block Na / K / Cl co transporter, - increase osmololality of urine - retains water in urine.
- Hypokalaemia (Na is able to reabsorb into blood later on but K+ relies on transport) - metabolic acidosis (K+ and H+ ions go hand in hand)
- Ototoxicity
Are loop diuretics quick or slow acting
Relatively quick - 30mins IV, 60 mins oral
Where to thiazide - diuretics act, give 3 examples
Indapamide, bedroflumethiazide, metalozone
Act at distal convoluted tubule (DCT)
How do thiazide diuretics work - relate this to their potential initial SE
Block Na reuptake into plasma, increasing urine osmolality so drawing out more water in urine.
Can cause hyponatraemia as excreting more Na+
Why do thiazide-diuretics also cause hypokalaemia
Initially they increase urine Na+ , but further down tubule this high level of Na+ reabsorbs into plasma, K+ is exchanged for this into urine so get low K+ plasma levels.
Other than hyponatraemia and hypokalaemia what other SE of 2 things is caused by thiazides
Hyper calcaemia Increased urate (avoid in gout)
Give 2 examples of potassium sparing diuretics, where and how do they work, how can this lead to a SE
Spironolactone, Eplerenone
Aldosterone receptor blockers - prevent aldosterone (mineralocorticoid produced by adrenal gland) acting on kidney. Therefore salt re-absorption into plasma is stopped, so have high urine Na+ levels - water drawn out via osmosis, but means get incr. plasma K+ levels - hyperkalaemia SE (also metab acidosis as K+ and H+ go hand in hand).
How long does spironolactone and eplerenone take to work
Days
