If not, dilute urine passes through collecting duct and is excreted in large amounts. Increases permeability of the luminal membrane to water. B. Pressor effect . Pressor effect requires much higher concentrations than antidiuretic effect. Acts directly on vascular smooth muscle to cause vasoconstriction .
Physiological importance is complicated by the presence of various cardiovascular reflexes.
C. Receptor subtypes . Identified using vasopressin analogs . V 1 receptors . V 2 receptors . Renal tubular cells.