Target Cell Polarity and Membrane Phosphorylation in Relation to the Mechanism of Action of Antidiuretic Hormone

The plasma membrane of the bovine renal collecting duct epithelial cell has been resolved into its apical (luminal) and basal-lateral (contraluminal) components by free flow electrophoresis. The contraluminal, but not the luminal, membrane was found to contain antidiuretic hormone-sensitive adenylate cyclase. The luminal membrane was found to contain a cyclic 3':5'-adenosine monophosphate-sensitive self-phosphorylating system consisting of a membrane-bound protein kinase and its membrane-bound substrate(s); this intrinsic protein kinase was not present in the contraluminal membrane. These findings provide direct evidence that the initiating steps in the action of antidiuretic hormone on the kidney take place at the contraluminal pole of the hormonesensitive target cell and that the late or terminal steps occur at the luminal pole, where they involve an alteration in the level of membrane phosphorylation.