Distal Convoluted tubule Flashcards
(24 cards)
How much of the water and sodium was reabsorbed in the PCT?
65% water 65% sodium
How much water and sodium is entering the distal convoluted tubule?
20% water
10% of sodium ions
What is the osmolality entering the distal convoluted tubule?
100-200 mosm
How can we divide the distal tubule?
Early DT and late DT
What specialised transporters are in the early DT?
Specialised transporters on the luminal membrane
Another sodium potassium atp channel on the basolateral membrane (2 K in 3 Na out)
What other ions apart from Na and H2O are in the DCT?
Chloride ions
Calcium
What is the concentration of Na in the luminal tubule compared to the inside of the cell?
It is higher than inside the cell
Therefore sodium ions flow through the transporter on the luminal membrane into the cell
What is also transported with sodium into the cell?
Chloride ions
What is the name of the sodium chloride transporter?
Sodium Chloride Symporter
because its moving in the same direction
What happens to the chloride in the cel?
Special channel allows chloride to get pumped into the blood
Out of the 10% of sodium that enters the distal convoluted tubule, how much is reabsorbed via the sodium chloride symporter?
5-6% in the early distal tubule
How is calcium reabsorbed when blood calcium is low?
PTH (parathyroid hormone) is released by the PT gland
This PTH receptor is on the DCT cell
What happens when PTH binds to the DCT receptor
Activates a secondary mechanism
G stimulatory protein,
bind to GTP, activates adenyl cyclase that can convert ATP into cAMP,
cAMP activates protein kinase A
What does the protein kinase A do?
Calcium modulated channels activated by protein kinase A stimulation (phosphorylating them)
Calcium is sucked into the cell
What happens to the calcium inside the cell?
Small proportion binds to calbindin
Most goes into the blood
How does calcium go into the blood from the cell? method 1
Calcium in low conc. inside cell, blood levels of calcium is higher
Has to go against conc. gradient to leave
Proteins on the basolateral membrane help pump calcium out, and bring sodium in
Secondary active transport
How does calcium go into the blood from the cell? method 2
Calcium is pumped against concentration gradient, Protons H+ brought into the cell.
Needs ATP
Drugs that inhibit sodium chloride symporter
Thiazide diuretic
prevents salt and water reabsorption
What occurs in the late distal tubule?
Reacts to aldosterone (which is produced in the adrenal cortex)
Stimuli for aldosterone production
Angiotensin II
Sodium drop, potassium peak
(Hyponatremia, hperkalemia)
Why is aldosterone able to pass the lipid bilayer and what is the effect of this?
Steroid hormone,
Stimulates genes, activates transcription factors
What proteins are produced as a consequence to aldosterone activation?
A: basolateral protein, sodium potassium pumping protein, adds sodium to blood solving hyponatremia
B: Luminal protein, allowing sodium ions into the cell due to low sodium conc. inside of the cell
C: luminal protein, Secretes potassium out into urine, due to hyperkalaemia.
B and C needs no atp
A needs ATP
What is interesting about the late distal tubule?
It is very specific
Dependent upon hormones
What is another hormone that can be present here and what is its affect
ADH can act on these DCT cells, creating pores (aquaporins) for water reabsorption
Water follows the salt (osmosis following)
(increases blood pressure)
CAN act in DCT but not always
