effect of ADH on kidney

• Effect of ADH on kidneys (low blood water potential)

  • Water is reabsorbed by osmosis
  • Reabsorption occurs in collecting ducts
  • ADH increases permeability of collecting duct cells
  • ADH increases number of aquaporins
• Effect of ADH on water reabsorption

  1. Collecting duct contains vesicles with aquaporins

  2. Activates aquaporins

  3. Vesicles fuse with luminal membranes

  4. Increases membrane permeability to water
• As filtrate travels along the collecting duct

  Water moves from collecting duct to tissue fluid and blood plasma
• As the filtrate in the collecting duct loses water it becomes more concentrated
• A small volume of concentrated urine is produced, flows from the kidneys through the ureters and into the bladder
• If water potential is too high

  The opposite happens
• Osmoreceptors

  Cells in the hypothalamus that detect water potential
• If osmoreceptors are not stimulated, no nerve impulses are sent to the posterior pituitary gland
• No ADH is produced
• Aquaporins


  Water permeable channels in collecting duct cells
• Aquaporins are moved out of the luminal membranes of collecting duct cells
• Collecting duct is no longer permeable
• Filtrate flows along but loses no water and is very dilute
• A large volume of dilute urine is produced
• diagram of Wp