TY - JOUR T1 - Mechanism of Secretion from the Adrenal Medulla JF - Molecular Pharmacology JO - Mol Pharmacol SP - 60 LP - 68 VL - 5 IS - 1 AU - O. H. VIVEROS AU - L. ARQUEROS AU - R. J. CONNETT AU - N. KIRSHNER Y1 - 1969/01/01 UR - http://molpharm.aspetjournals.org/content/5/1/60.abstract N2 - The subcellular distribution of dopamine β-hydroxylase in homogenates of rabbit adrenal glands has been measured to determine the possibility of using the enzyme as a marker to trace the fate of the catecholamine storage vesicle membranes following secretion of adrenaline. Optimal conditions for the assay of the enzyme in each of the subcellular fractions have been determined. These studies show that a large fraction of the total dopamine β-hydroxylase activity of the adrenal glands is present in the 26,000 x g supernatant fraction. Most of the enzyme activity associated with the particulate fraction was retained in the particles when they were washed with sucrose. When the particles were washed with distilled water, however, a large proportion of the enzyme activity was obtained in the supernatant fraction but a significant amount remained in the particulate fraction, indicating that the enzyme was contained within vesicles in both a soluble form and a membranebound form. The distribution of adrenaline and dopamine β-hydroxy1ase in a sucrose density gradient showed a peak of dopamine β-hydroxylase activity near the bottom of the gradient closely associated with the adrenaline storage vesicle fraction, and a second peak near the top of the gradient associated with a less dense particulate fraction. ER -