How does ADH work and what does it do?

A. It binds to the collecting tubules in the kidney, opening pores to allow water to flow back out of the kidney into the blood.

B. It binds to blood cells, making them more porous to water so it more easily diffuses back into them and is not lost in urine filtration.

C. It binds to water molecules, making them too large to diffuse out of the blood stream, retaining water when the body needs it.

D. It binds to nerve cells in hypothalamus, signaling that the body is dehydrated and should retain water.

E. It binds to the kidney tubules, making them less porous to water so less water filters out.

The correct answer will be option-A.

Explanation:

ADH or anti-diuretic hormone is a chemical messenger produced by the hypothalamus in response to the water level in the blood, maintain blood pressure.

ADH is released in response to the osmolarity of the blood that is a low amount of water which is perceived by the osmorecpetors in neurons. The low level of water leads to the production of ADH from neurons which binds to the ADH receptors in the collecting tubules of the kidneys.

They allow insertion of aquaporins-2 in the membrane which allow re-absorption of the water to maintain the water level of the body.

Thus, option-A is the correct answer.