L28 - Kidney - Urine pH And Drug Excretion Flashcards
What are the key functions of the nephron in the kidney? (3)
- glomelular filtration
- tubular secretion
- tubular reabsorption
What are the possible routes for substances entering nephron? (3)
- parital filtering, mostly secreted, fully excreted
- partial filtering, partial reabsorbed, partially excreted
- partial filtering, fully reabsorbed, not excreted
How do you calculate amount excreted?
Amount excreted = amount filtered + amount secreted - amount reabsorbed
What are not excreted by kidneys?
Whole proteins and protein based drugs
What is proteinuria?
high levels of protein in urine
What does carbonic anhydrase do?
Key enzyme in acid-base homeostasis
What does adding/subtracting carbonate (HCO3-) do?
Lower/raises H+ by influencing this equation
CO2 + H2O <-> H2CO3 <-> HCO3- + H+
What does the kidney regulate in terms of body pH?
HCO3-
- thereby pH
What is the carbonate reabsorption? (4)
- cabonic acid in tubular cell breaks down into H+ and HCO3-
- H+ to tubules, combines with HCO3-
- HCO3- transported into body
- filtered HCO3- disappears, HCO3- generated inside cell enters the body
What is the net result of carbonate reabsorption?
no loss of HCO3-
What is the carbonate generation - H+ secretion? (3)
- carbonic acid generated in tubular cells
- H+ combines with filters HPO42- = excreted
- HCO3- transported into body
What is the net result of carbonate generation - H+ secretion?
Gain of HCO3-
What is the carbonate generation - glutamine metabolism? (4)
- glutamine enters tubule cells (filtrate or blood plasma)
- metabolised inside cells to ammonia (NH4+) and HCO3-
- NH4+ secreted into tubules and excreted
- HCO3- transported into body
What is the net result of carbonate generation - glutamine metabolism?
Gain of HCO3-
What is akalosis?
When the body loses H+, pH increases becoming more alkali
What is acidosis?
When the body gains H+, pH decreases becoming more acidic
What is the body’s response to acidosis? (2)
- H+ secreted into tubules (all filtered HCO3- reabsorbed, additional HCO3- absorbed, H+ excreted bound to phosphate)
- glutamine metabolism enhanced = more HCO3-
What is the body’s response to alkalosis? (2)
- H+ secretion into tubules, cannot keep up with filtered HCO3- (excess excreted)
- glutamine metabolism decreased = reduced HCO3- gen
What drugs are ionised in alkaline urine?
Acidic drugs are ionised
What drugs are ionised in acidic urine?
alkaline drugs are ionised
What drugs are less likely to be reabsorbed in the kidney?
ionised drugs
- increased excretion
What happens in aspirin poisoning? (2)
aspirin needs to be quickly removed from the body
- IV indusion of sodium bicarbonate
- enters urine, raises pH
What happens to aspirin’s active metabolite? (2)
salicylic acid becomes ionised
- reducing its absorption
- aspirin excreted quicker = lowers plasma conc
