When healthy young men eat very little salt, their kidneys rely more on a specific sodium pump (ENaC) in the final part of the kidney to hold onto sodium — and blocking that pump removes as much sodium as blocking the earlier pump.

When healthy young men eat very little salt, their kidneys rely more on a specific sodium pump (ENaC) in the last part of the kidney to hold onto sodium — but when they eat a lot of salt, that pump becomes less important.

When you eat a lot of salt, your kidneys use the first part of the filtering tube (DCT) to hold onto sodium; when you eat little salt, they switch to a different part (collecting duct) that’s controlled by a hormone called aldosterone.

When you eat little salt, your kidneys rely more on a specific channel (ENaC) to hold onto sodium — so blocking it with amiloride makes you pee out a lot more salt. When you eat a lot of salt, that channel isn’t as important, and another part of the kidney (DCT) handles most of the sodium.

When healthy young men eat a lot of salt, their kidneys use the part of the tubule that thiazide drugs target to reabsorb more sodium — so when you give them a thiazide, it works way better at making them pee out salt.

When healthy young men eat a lot of salt, their kidneys use the DCT part more to reabsorb sodium — even though the sodium pump in that part becomes less active — because more sodium is being filtered and pushed through.