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Can someone explain why it is that aldosterone causes a negative lumen potential in the collecting duct with K+ excretion when the K+ backleak in the TAL causes a positive lumen potential?
Clearly there's something I'm missing here. I would think the CD would have a positive lumen. Is there some step-wise change? It looks like first aid is saying Na reabsorption occurs first, creating a negative lumen, which will then result in K+ and H+ excretion whereas the TAL has a + lumen because Na/K/2Cl creates a concentration gradient favoring K back leak.
Clearly there's something I'm missing here. I would think the CD would have a positive lumen. Is there some step-wise change? It looks like first aid is saying Na reabsorption occurs first, creating a negative lumen, which will then result in K+ and H+ excretion whereas the TAL has a + lumen because Na/K/2Cl creates a concentration gradient favoring K back leak.
