ADH has two actions, one on the kidney and the other on vascular smooth muscle, these actions are mediated by different receptors, different intracellular mechanisms, and different secondary messengers.a. The major action of ADH is to increase the water permeability of principal cells in the late distal tubule and collecting duct.b. The receptor for ADH on the principal cells is a V2 receptor, which is coupled to adenylyl cyclase via a Gs protein. c. The second messenger is cAMP, via phosphorylation steps, directs the insertion of water channels, aquaporin 2 (AQP2), in luminal membranes.d. The receptor for ADH on the principal cells is a V1 receptor, which is coupled to phospholipase C via Gq protein.Which one of the following combination of above statements is correct? -triyambak.org