Distribution and properties of adrenergic storage vesicles in nerve terminals

The subcellular distribution of adrenergic storage vesicles was determined in rat spleen, heart and superior cervical ganglion and in dog spleen using dopamine-beta-hydroxylase (DBH) as a marker for vesicle membranes and norepinephrine (NE) as a marker for the soluble contents of the storage vesicles. Density gradient centrifugation revealed populations of vesicles in the rat heart and spleen with equilibrium densities of 1.05 and 1.15 g/ml. There was a consistent shoulder on the low-density peak at a density of 1.08 g/ml. Several populations of NE-and DBH-containing vesicles were also found in homogenates of dog spleen. In homogenates of superior cervical ganglia, most of the NE was nonsedimentable while the DBH activity formed a broad poorly resolved band within the gradient. Although NE and DBH were present in each of several populations of vesicles in nerve terminals of rat and dog organs, the ratio of NE/DBH varied as a function of the species and organ examined. Mitochondrial contamination did not, as has been previously claimed, influence the distribution of DBH which was observed. Both light and heavy vesicles were able to take up and retain NE-[3H].