Epithelial Transport Solutes Flashcards
What happens to K+ after it is pumped into cell via Na/K pump?
a lot of it moves back out across the basolat side of the epi cell due to K+ channels that transport passively down concentration gradient
Where is the Na/K pump located on epi cells?
basolateral
How is glucose absorbed in epi cells?
SGLT2 across apical (1 Na: 1 Glucose)
Na/K and K channels active on baso
GLUT channel on baso transports glucose out to ECF
*can’t use SGLT transporter on baso side because Na concentration gradient in opposite direction
How is sodium absorbed in epi cells?
e.g collecting tubule in kidney
ENaC channel on apical moves Na+ into cell
Na/K pump on baso side pumps it out
*Get a net positive charge in the ECF so can have passive Cl transport through the tight junctions (paracellularly) = NET absorption of Cl and Na
How is K+ secreted in epi cells?
Na/K pump on baso side moves K into cells (some K still moves out through baso side)
K channels on apical side lets some K pass (ENaC still active, if ENaC is blocked, no K movement)
*Cl- still can move through tight junctions laterally
How is chloride secreted in epi cells?
Na/K pump and K channels active on baso side
NKCC1 secondary active transport on baso side moves 1Na, 1K and 2Cl into cell
CFTR channel on apical side moves chloride out, get a build up of chloride out so Na+ can move out paracellularly
How do you get transport of isoosmotic solutions?
1) areas of the lateral sides of the cells near tight junctions might not be isotonic
2) could be gradients we can’t measure (i.e not really isotonic) and so many aquaporins that anything that is not exactly isotonic moves
