Effects of various agents on the Mg2+-ATP stimulated incorporation and release of catecholamines by isolated bovine adrenomedullary storage vesicles and on secretion from the adrenal medulla

The effects of several agents on the Mg 2+ -ATP stimulated incorporation and release of catecholamines by isolated bovine adrenomedullary storage vesicles suggest that both of these processes may employ a similar or identical set of reactions for a portion of their respective pathways. N -ethylmaleimide and N - N -di-isopropyl- N ′-isoamyl- N ′-diethylaminoethylurea (P-286) inhibited equally both incorporation and release. Prenylamine inhibited incorporation to a greater extent than it inhibited release. Reserpine and propranolol, at concentrations which almost completely blocked incorporation, had little or no effect on release. N -ethylmaleimide, P-286 and prenylamine, when present in the perfusion medium at concentrations which blocked release from isolated vesicles, also blocked the secretory response of the isolated perfused adrenal gland to acetylcholine. In isotonic salt solutions, Mg 2+ plus ATP stimulates to an equal extent the release of both soluble dopamine-β-hydroxylase and catecholamines. An hypothesis is proposed to explain these observations and to serve as a model for additional experiments.