The cells of PCT pretty much like all cells of our body have inside of them a low concentration of Sodium, because of the presence of Na/K ATPase which take out Sodium from the cells into the interstitial space.
Now because the cells of PCT have a lower concentration of Sodium, they can easily suck in Sodium, so where should Na/H exchanger take Sodium? Simple, Into the cells.
Now where should Hydrogen go?
For any exchanger to fucntion without using energy it becomes imperative that it doesn't lead to the transfer of net charge into or out of the cells. So if Sodium is going into the cells and because both of are positively charged, where should Hydrogen go? Out of the cells.
Na/H exchanger leads to the movement of Sodium into the cells and causes the movement of Hydrogen into the luminal space, from where Hydrogen ions get excreted out of the body as urine. The exchanger is intimately related to preservation of Bicarbonates, HOW?
It can seen that in the reaction?
H2CO3 <==> H+ + HCO3-
The disassociation of Carbonic acid dominates in the PCT, while the opposite is true is in the luminal space, why is it so?
It is because There is less of H+ in the cells of PCT while there is more of H+ in the luminal space because of Na/H exchanger, so you can apply Le--Chatelier' s principle and understand the role played by Na/H in the reabsorption of Bicarbonates.
If you don't know what it is I highly recommend that you check it out because it is a fairly important yet simple concept.
-Syed Moris
To read more of such write-ups - click here
Now because the cells of PCT have a lower concentration of Sodium, they can easily suck in Sodium, so where should Na/H exchanger take Sodium? Simple, Into the cells.
Now where should Hydrogen go?
For any exchanger to fucntion without using energy it becomes imperative that it doesn't lead to the transfer of net charge into or out of the cells. So if Sodium is going into the cells and because both of are positively charged, where should Hydrogen go? Out of the cells.
Na/H exchanger leads to the movement of Sodium into the cells and causes the movement of Hydrogen into the luminal space, from where Hydrogen ions get excreted out of the body as urine. The exchanger is intimately related to preservation of Bicarbonates, HOW?
It can seen that in the reaction?
H2CO3 <==> H+ + HCO3-
The disassociation of Carbonic acid dominates in the PCT, while the opposite is true is in the luminal space, why is it so?
It is because There is less of H+ in the cells of PCT while there is more of H+ in the luminal space because of Na/H exchanger, so you can apply Le--Chatelier' s principle and understand the role played by Na/H in the reabsorption of Bicarbonates.
If you don't know what it is I highly recommend that you check it out because it is a fairly important yet simple concept.
-Syed Moris
To read more of such write-ups - click here
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