Renal Question: Help?

[Turtlez]

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Ok, can someone please explain the following sentence from first aid's diuretics section?

In low K state, H (rather than K) is exchanged for Na in cortical collecting tubule, leading to alkalosis and "paradoxical aciduria"

What is the mechanism behind this paradoxical aciduria? Much thanks!

 

[Brain Bucket]

...you just explained it. The Na/H pump is favoured over the Na/K pump. Maybe I'm missing something? Are you asking why it's paradoxical? Something else?

 

[dyspareunia]

Ok, can someone please explain the following sentence from first aid's diuretics section?

In low K state, H (rather than K) is exchanged for Na in cortical collecting tubule, leading to alkalosis and "paradoxical aciduria"

What is the mechanism behind this paradoxical aciduria? Much thanks!

The mechanism is the Na/H exchanger. It's paradoxical because in the presence of an alkalosis you would expect an alkalotic urine.

 

[Turtlez]

is the Na/H exchanger on the lumen side?

 

[Robotic Dock]

Hi

Means that when K+ is low in blood, H+ from blood is exchanging for K+ from the cells done by a pump exchanger. This also happens in kidney collecting tubule and that is why you lose H+ in the urine, PARADOXICALLY, to save blood K+, not to get rid of the acid. Result is metabolic alkalosis+paradoxical aciduria.

 

[Nephronlearner]

Concentration of K+ in plasma is related to NH3 synthesis, with hypokalemia stimulating NH3 synthesis which leads to excretion of H+ as NH4+ in urine. Excreting H+ from plasma leads to alkalosis.
Another possible explanation may be related to the H-K exchanger which can be bidirectional, thereby if you have low H+ in the blood, the exchanger will add H+ to the blood, while taking K+ inside the cell and the other way around. So low K+ could be corrected by exchanging it for H+ leading to excess H+ in the urine and lower H+ in the blood.