Secretion Flashcards
Where does secretion take place
FROM the peritubular capillaries INTO the tubule lumen, providing a second route into the tubule.
For what substances and why is secretion important
Important for substances that are protein-bound, since filtration at glomerulus is very restricted
Allows harmful substances to be excreted quicker
A common problem with carrier mechanisms
They’re not very specific
The organic acid mechanism, which secretes lactic and uric acid, also secretes penicillin, aspirin and PAH (para-amino-hippuric acid).
What does the organic base mechanism excrete, on purpose and accidentally
Choline, creatinine etc
Accidentally morphine and atropine
K+, cation or anion and its normal concentration in ECF
Major cation
~4mmoles/l
What concentration of K+ is considered hyperkalaemia and what’s its effects
> 5.5mmoles/l
Decreases resting membrane potential of excitable cells and eventually ventricular fibrillation and death.
What concentration of K+ is considered hypokalaemia and what’s its effects
<3.5mmoles/l
Increases resting membrane potential ie hyperpolarizes muscle, cardiac cells => cardiac arrhythmias and eventually death.
What happens to K+ that is filtered at the glomerulus
Reabsorbed, primarily at the proximal tubule
Increased renal tubule cell [K+] results in
Increased secretion of K+
Decreased renal cell tubule [K+]results in
Decreased secretion of K+
What hormone regulates the excretion of K+ and it’s effect on excretion
Aldosterone
Increased aldosterone = increased secretion of K+
What hormone regulates Na+ reabsorption and what’s its effect on reabsorption and where does this take place
Aldosterone
Increased aldosterone = increased reabsorption of Na+ at the distal tubule
