Tubular Transport Flashcards
Convoluted proximal tubule
Actively reabsorb: 85% bicarb, 85% NaCl, 65% K (paracellularly), 100% glucose and AA
Passively reabsorb: 60% water
Straight proximal tubule
Secrete acids, bases and drugs from blood stream
Na/K ATPase
Maintain low intracellular sodium in PT to encourage Na in from lumen and H out
**Located in all parts of nephron
CA (carbonic anhydrase)
H meets with bicarb to form H2CO3
CA dehydrates H2CO3 to H2O and CO2 so it may enter the cell then it rehydrates
**Leads to bicarb reabsorption
Thin descending loop
Water reabsorption (not permeable to ions)
Thin ascending loop
Relatively impermeable to ions and water
Thick ascending loop
Impermeable to water, reabsorb 25% Na
NKCC2 (Na/K/2Cl transporter)
Reabsorb sodium, potassium and twice the chloride back in to cell
High intracellular K in loop
K diffuses back out creating (+) luminal potential
Mg and Ca enter blood paracellularly
Distal convoluted tubule
10% NaCl reabsorbed
Mostly impermeable to water
NCC
Na and Cl cotransporter
DCT calcium channel
Acted on by PTH
Collecting tubule
*Most important site for potassium secretion - the more sodium delivered to the CCT, the more potassium is secreted
Principle cells: Na in, K out
Intercalated cells: H out
ENaC
Brings Na in, encourages K out
Aldosterone
Increase ENaC and Na/K ATPase
Na in, K out
Hypokalemia, alkalosis
