There are, broadly speaking, 5 different categories of diuretics. I have put them in order of where they act in the nephron. I suppose the main characteristic of most diuretics is that they act to allow water to stay within the tube that leads out to the ureter. The more concentrated with ions that the solution within the tube is, the more it will hang on to water - so by inhibiting the symporter mechanisms that remove the ions from the tubular fluid, you hold water within the tube allowing it to be passed out. However, the actions of aldosterone, angiotensin 2, and ADH also have large roles to play with the reabsorption of water.
ADH is a neurohypophyseal hormone also known as vasopressin. It increases water permeability of the collecting duct and distal convoluted tubule by inducing translocation of aquaporin-CD water channels in the plasma membrane of collecting duct cells. It also increases peripheral vascular resistance, which in turn increases arterial blood pressure.
Aldosterone, a steroid hormone, is the main mineralocorticoid hormone. Interestingly, it responds to potassium levels, likely stimulated by the carotid sensors. Aldosterone tends to promote Na+ and water retention, and lower plasma K+ concentration by the following mechanisms:
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