Which of the following regulates the transfer of iron from the enterocyte into the plasma?

The regulation of iron transfer from enterocytes into the plasma is primarily controlled by ferroportin. This protein acts as a channel on the basolateral membrane of enterocytes, where iron is released into the bloodstream. Hepcidin, a hormone produced by the liver, plays a critical role in this process by regulating ferroportin.

When iron levels in the body are adequate or high, hepcidin is released, which binds to ferroportin and causes its degradation. This action decreases the amount of iron that enters the plasma because ferroportin is no longer available to transport iron out of the enterocyte. Conversely, when iron levels are low, hepcidin production decreases, leading to increased ferroportin levels and enhanced iron absorption into the plasma.

Therefore, while hepcidin itself does not directly transfer iron, it is the key regulator of ferroportin activity, which ultimately controls the transfer of iron into the bloodstream. This regulatory mechanism ensures that the body maintains iron homeostasis effectively.