Final answer:
The renin-angiotensin-aldosterone mechanism is the most important trigger for aldosterone release, which occurs in response to low blood pressure and results in increased Na+ reabsorption and water retention, raising blood pressure.
Step-by-step explanation:
The most important trigger for aldosterone release is the renin-angiotensin-aldosterone mechanism. This mechanism is activated when blood pressure drops, which stimulates cells in the juxtaglomerular apparatus of the kidney to release renin. Renin then reacts with angiotensinogen to produce angiotensin I that is converted into angiotensin II. Angiotensin II functions as a hormone that causes the adrenal cortex to release aldosterone, leading to increased Na+ reabsorption, water retention, and a subsequent increase in blood pressure.