ADH function

• ADH binds to receptors on membrane of tubules
• ADH is a 1st messengers
• ADH stimulates the activation of cAMP, which then activates an enzyme
• cAMP is a 2nd messenger
• the activated enzyme causes vesicles containing aquaporins to fuse with tubule membrane
• aquaporins are proteins that form the water channels
• aquaporins make tubule membrane more permeable to water
• water moves out of the tubule into the tissue fluid in medulla and capillaries