18 K+ and more!:) Flashcards
What is the intracellular concentration of K+?
140mM
What is the extracellular concentration of K+/
4mM
How can any adverse affects of increased extracellular K+ be avoided?
buffering by uptake into cells
What 6 things might cause hyperkalaemia?
CKD 5 crush injuries blood transfusion cytotoxic drugs insulin deficiency over use of K+ sparing diuretics
Why might blood transfusion cause hyperkalaemia?
red cells leak some K+ into the plasma during storage
Why might giving glucose treat hyperkalaemia?
stimulates insulin release
insulin stimulates Na+/K+ ATPase
cells uptake K+
Name 3 causes of hypokalaemia
diarrhoea furosemide (along with most diuretics) insulin overdose
what might you do if someone is have significant furosemide-induced hypokalaemia?
decrease the concentration of furosemide and increase concentration of K+ sparing diuretic
name a K+ sparing diuretic
sprinolactone
What is the main dangerous consequence of hypo or hyperkalaemia?
dysrhythmia
How might you treat hypokalaemia?
give IV K+ if acute
give orally if chronic
How is K+ exchanged in the TAL?
through NKCC cotransporter
much of the K+ cycles back into the filtrate here though
How is K+ exchanged in the DCT and CD?
apical membrane K+ channel (ROMK) (aldosterone)
A Ca2+ activatead K+ channel (flow rate dependent)
What is aldosterone secretion sensitive to?
AngII
K+
What is the main hormone for regulating bodily K+?
aldosterone
What proportion of total Ca2+ is filtered by the glomerulus?
10% total
20% free
what happens to filtered calcium in the PCT?
moves transcellularly
proportional to H2O movement
What happens to filtered calcium in the TAL?
absorbed
driven by + potential in the lumen of the TAL
Why is there a positive potential in the TAL lumen?
MKCC is electrically neutral
apical K+ recycling makes the filtrate +
this drives the reabsorption of Ca2+
How does ascending to high altitudes affect red cell production?
it increases it
where is EPO made?
renal mesangial cells
What is another name for mesangial cells?
peritubular fibroblasts
What stimulates transcription of EPO?
hypoxia-inducible factors (HIF-2)
What is HIF-alpha degradation enhanced by?
Fe2+
How does iron affect EPO?
low iron causes EPO production
How is EPO regulated?
EPOR binds and internalises EPO
how does renal failure lead to anaemia?
what is the exception to this?
falls in EPO production
polycystic kidney disease
How does polycystic kidney disease not cause anaemia?
sufficient renal parenchyma to prevent loss of EPO production
What EPO analogue is used clinically?
Darbepoietin alpha
Can EPO be found in urine
yes, a little bit as it is 34kDa
What is the other name for vitamin D?
cholecalciferol
How is vitamin D metabolised?
converted to 25-hydroxycholecalciferol in the liver
converted to 1,25-hydroxycholecalciferol by the kidney
What are the actions of 1,25-VitD?
increase Ca2+ and phosphate absorption in the ileum
decrease Ca2+ and phosphate excretion
