Final answer:
An aldosterone antagonist reduces sodium and water retention by blocking the effects of aldosterone, which normally promotes reabsorption of sodium and water in the kidneys.
Step-by-step explanation:
The nurse should explain to a patient in heart failure that an aldosterone antagonist works by reducing sodium and water retention. Aldosterone is a hormone that increases the reabsorption of sodium and water into the bloodstream, thus increasing blood volume and pressure. An aldosterone antagonist blocks this effect, thereby promoting the excretion of sodium and water, which can alleviate the symptoms of heart failure.
In more detail, aldosterone normally acts on the distal convoluted tubules and collecting ducts of the kidneys, where it stimulates the sodium-potassium pump. This pump reabsorbs sodium (Na+) back into the bloodstream and removes potassium (K+) from the blood by excreting it into the urine. As a result, water follows the reabsorbed sodium through osmosis, leading to increased blood volume. Aldosterone antagonists effectively prevent this reabsorption, leading to a reduction in blood volume and pressure, which is beneficial in managing heart failure.
In summary, the correct explanation for how an aldosterone antagonist works would be option:
- Reducing sodium and water retention