The hormone that promotes reabsorption of water from glomerular filtrate is vasopressin.

Vasopressin, also known as antidiuretic hormone (ADH), is a hormone produced by the hypothalamus and released by the posterior pituitary gland. Its primary function is to regulate water balance in the body by promoting water reabsorption in the kidneys.

Here is a detailed explanation of how vasopressin promotes water reabsorption:

1. The process starts in the hypothalamus, where specialized cells called osmoreceptor cells detect changes in blood osmolarity. These cells monitor the concentration of solutes in the blood, specifically sodium.

2. When blood osmolarity increases, indicating dehydration or an increase in solute concentration, the osmoreceptor cells in the hypothalamus are stimulated.

3. As a response, the hypothalamus signals the posterior pituitary gland to release vasopressin into the bloodstream.

4. Vasopressin then travels to the kidneys, where it acts on the cells of the renal tubules, specifically the collecting ducts.

5. In the collecting ducts, vasopressin binds to receptors on the surface of cells, triggering a cascade of molecular events.

6. This cascade leads to the insertion of water channel proteins called aquaporins into the apical membrane of the collecting duct cells. Aquaporins allow water molecules to move freely across the cell membrane.

7. With the presence of aquaporins, water can now be reabsorbed from the glomerular filtrate and into the surrounding interstitial fluid.

8. From the interstitial fluid, water can then be reabsorbed into the bloodstream by osmosis, effectively conserving water and preventing excessive loss through urine.

9. The reabsorption of water from the glomerular filtrate back into the bloodstream helps maintain proper water balance in the body, preventing dehydration.

In summary, vasopressin promotes the reabsorption of water from the glomerular filtrate by increasing the permeability of the collecting ducts to water through the insertion of aquaporins. This mechanism allows the body to conserve water and maintain proper water balance.

Vasopressin that is also called antidiuretic hormone released by hypothalamus for controlling the water and electrolyte balance in the kidney at the renal cortex.