Final answer:
An increased aldosterone level is the factor that increases potassium excretion by the kidneys, by stimulating the sodium-potassium pump and increasing renal filtration of potassium.
The correct option is A.
Step-by-step explanation:
The factor that increases potassium excretion by the kidneys is an increased level of aldosterone. Aldosterone is a hormone that regulates the balance of sodium and potassium in the body. When aldosterone levels are high, it causes the kidneys to reabsorb more sodium from the filtrate in the distal convoluted tubules and collecting ducts, and simultaneously increases the excretion of potassium.
This is because aldosterone stimulates the sodium-potassium pump, leading to more sodium being reabsorbed into the bloodstream and more potassium being secreted into the renal filtrate for excretion.
Aldosterone secretion can be triggered by various conditions, including increased levels of potassium in the blood, severely decreased levels of sodium, or decreased blood pressure.
Once released, aldosterone works to conserve water and increase plasma water levels by reducing sodium excretion from the kidneys. Additionally, the effect of aldosterone on sodium and water reabsorption lead to an increase in blood volume. Conversely, it promotes the expulsion of excess potassium to maintain electrolyte balance.
The correct option is A.