solute recovery W1 Flashcards
4 parts of the nephron?
renal corpuscle
proximal tubule
Henle’s loop
distal tubule
difference between proximal and distal tubules - histology?
proximal tubules have microvilli, distal tubules do not.
proximal tubule structure?
lumen (apical side)
microvilli
tight junctions between cells (quite leaky in prox tubule)
basement membrane
basal side
things that the nephron epithelia have to recover?
sodium
potassium
calcium
magnesium
chloride
bicarbonate
phosphate
water
amino acids
glucose
proteins
what parts in the proximal tubule allow recovery of molecules?
primary active transporters
solute carrier family proteins
aquaporins
ion channels
protein endocytosis receptors
common primary active transporters in the proximal tubule plasma membrane?
Na_/K+ ATPase
H+ ATPase
solute carrier family proteins - many of these are what? (proximal tubule)
co-transporters powered by established conc gradients (eg in Na+, ‘secondary active transporters’
what are aquaporins?
water channels
just let water flow - nothing active
sodium potassium ATPase - location and function on cell (proximal tubule)?
located on basal side
active export of Na+ from cell:
2K+ in, 3Na+ out, ATP->ADP+Pi
this creates high sodium in lumen, low sodium in cell. this powers other transport
what allows sodium recovery in the proximal tubule?
Na+/H+ exchanger:
Na+ in, H+ out
what allows sodium recovery in the distal tubule?
sodium chloride co-transporter:
Cl- in, Na+ in
what allows potassium recovery in the loop of Henle?
Na-K-Cl cotransporter:
2Cl- in, Na+ in, K+ in
what channels allow potassium out the cell?
ROMK (renal outer medullary K channel)
where does amino acid recovery occur?
proximal tubule
where does glucose recovery occur?
mostly proximal tubule, partially in loop of Henle
what channels allow glucose recovery?
dont have to remember names, remember ratios and molecules.
mostly cotransporter with 1:1 Na+:glucose ratio
also cotransporter with 2:1 Na+:glucose ratio
why is diabetes pee sweet!!
uptake systems have limited capacity - fluid flowing through proximal tubule is only there for so long.
too much glucose = total resorbed glucose reaches a threshold, leads to increased excreted glucose.
what are anions and cations
anions - negatively charged ions
cations - positively charged ions
organic cation transporters function? (OCTS)
allow passive movement in either direction
antiporter? for organic cations?
allows H+ in (after being removed by Na+/H+ exchanger), and organic cations are exported out
MDR1 pump?
multiple drug resistance 1 pump
active transport of organic cations out the cell
organic anion transporter proteins function? (OATPs)
transport larger and somewhat hydrophobic organic anions (including many xenobiotics)
examples of anions OATPs transport?
prostaglandins
cholate
ciprofloxacin
cyclic peptides
examples of anions OATs transport?
methotrexate
furosemide
penicillin
what kind of process is OATs transport? why?
push in, drift out - so entry is active, exit is passive.
gradient of alpha-ketoglutarate across the membrane.
SLC12A3: 3Na+ in, alpha-ketoglutarate in.
OAT1,2,3: alpha-ketoglutarate out, anions in.
what can cause toxic levels of anions?
weak drift out - leads to toxic levels of anions in the cell.
example of a OAT channel blocker? when is this given?
probenecid
given with anti-tumour therapy to stop kidneys taking up organic anions.
why must you take penicillin so often?
lost via OAT channels
what allows phosphate recovery in the proximal tubule?
cotransporter allows Na+ in, PO4^2- in
bicarbonate equation thingy
bicarbonate + H+ ->/<- carbonic acid.
carbonic acid ->/<- (via carbonic anhydrase) water + carbon dioxide
bicarbonate recovery?
CO2 enters cell, meets with H2O and ca to form carbonic acid. this becomes bicarbonate, H+, and the H+ replaces what was lost in the urine. 3 bicarbonate recovered via cotransport with Na+
no net change in pH
what happens if there is remaining H+ when the bicarbonate has been taken up? (aka body is in some sort of acidosis)
HPO4^2- picks up H+, becomes H2PO4-, leaves body in urine.
net change in pH as loss of H+
how does ammonium leave the body? (when body is short of bicarbonate)
ammonia and H+ form ammonium. this can occur inside or outside the cell.
ammonia comes from broken down glutamine
intercalated cells?
type A - throws H+ out the body
type B - throws H+ back into the body
type A throws Away
type B Brings it Back
how is calcium recovered
mainly paracellular (between cells - through ‘leaky’ junctions), passive, and driven by osmosis once urine is more concentrated.
how does water travel across the kidney cells
aquaporins (mainly aquaporin1)
protein uptake in proximal tubule cells?
large proteins such as Megalin. other proteins stick to outside and are brought into cell.
