How does distal delivery of sodium and volume increase potassium excretion?
Increased distal delivery of sodium allows reabsorption via the epithelial sodium channel (ENaC) in the late distal convoluted tubule, the connecting tubule, and the cortical collecting duct. Reabsorption of sodium generates a negative charge in the lumen, which enhances potassium secretion through the ROMK channels. With higher urine flow, the secreted potassium is diluted and washed away, maintaining a diffusion gradient leading to continued potassium secretion. While ROMK channels are activated under physiological conditions, the BK channels are activated by increased urine flow.