PCT and LoH Transport Flashcards
what are two modes of transport in epithelium of nephron?
transcellular and paracellular
what creates the luminal sodium gradient for reabsorption in the pCT?
basolateral Na/K ATPase pump keeps Na really low in epithelial cell
what is it considered when sodium moves into the luminal membrane following the gradient created by the pump in the basolateral membrane?
secondary active transport
name the four molecules that are co transported with Na through the luminal surface of the PCT
Cl
Glucose
Amino Acids
phosphate
what is an antiport that Na has on the luminal surface of the PCT?
H+ goes into lumen and Na goes into epithelial cells
name the luminal glucose sodium co transporter in the PCT
sodium dependent glucose transporter
name the basolateral membran glucose transporter in the PCT
glucose transporter
what is the baso lateral cotransporter that is present in the PCT
bicarb and sodium
how does water pass in luminal and out basolateral surface of PCT?
aquaporin 1
why does diabetes lead to glucose in urine?
glucose is freely filtered and the sodium dependent glucose transporters have a max number and glucose will remain in the urine and hold onto water
what are the two ways to reabsorb bicarbonate into the luminal part of the PCT?
either reclaim that of which has been secreted or use glutamine to make new bicarbonate
describe what happens to bicarb in the lumen of the PCT?
it is turned into CO2 and H2O because of the acidic environment and presence of carbonic anhydrase in the brush border enzymes
once bicarb is CO2 and H2O in the lumen of PCT, what can happen?
it can diffuse into the luminal surface of the epithelium
once CO2 and H2O are in the epithelium what occurs?
bicarb is remade by carbonic anhydrase and cotransported out of the basolateral membrane with sodium
what is glutamine turned into in the epithelial cell of the PCT?
NH4 and bicarb
what happens to the NH4 that is made in epithelial cells of the PCT?
it is secreted into lumen via Na/H+ antiporter on luminal surface of the PCT
what is the main mechanism of K+ reabsorption in the PCT?
solvent drag as it rides along with H2O in the paracellular transport
explain how urea re-absorption occurs in the PCT?
it passively follows its concentration gradient, but requires the movement of some water out of the PCT to make a greater concentration gradient for it to follow
what happens to urea when you decrease the GFR? why is this?
you get increased plasma levels because the filtrate spends more time in the PCTs where urea can be reabsorbed and you get high plasma urea and BUN levels
name three common things secreted in the PCT
end products of metabolism
pollutants
drugs
what is the mechanism of secretion in the PCT? why can this be a problem?
non specific transporters…so things can compete for the transporters and may get increasing conc if transporters are taken
what is the name of the transporter on the luminal side of the ascending loop of henle?
NKCC transporter
what molecules does the NKCC transporter transport into the medulla
sodium, potassium and two chlorides
on the luminal surface of the ascending loop of henle there is an important transporter that sends K+ into the lumen, what is its name?
ROMK channel
