Final answer:
The cellular mechanism of ADH action on the collecting ducts involves activation of adenylate cyclase, leading to aquaporins being inserted into the cell membrane and an increase in water reabsorption.
Step-by-step explanation:
The cellular mechanism of ADH (antidiuretic hormone) actions on water permeability of the collecting ducts involves the activation of adenylate cyclase and increased cAMP production. Upon the binding of ADH to the receptors on the principal cells of the collecting duct, aquaporins are inserted into the plasma membrane, leading to a dramatic increase in water reabsorption. This process increases the water permeability of the cells, allowing for more water to pass from the urine into the bloodstream, thus concentrating the urine and regulating blood osmolarity and blood pressure.