the mechanism you cite for diuretics is not correct. It's been clear for decades that diuretics ACUTELY eliminate fluid and sodium but when taken regularly fluid and sodium levels in the body equilibrate back at exactly the levels they were at pre-diuretic. If you look at the medical literature of the last few years you'll see that diuretics (thiazide type, used for hypertension) are thought thought to perhaps have effects on vascular endothelial cells to reduce BP, but sodium and fluid balance are very clearly not the way they help keep BP down. Many feel their mechanism for lowering BP is simply not yet understood.
"I may be synthetic but I'm not stupid"
Bishop, in "Aliens"