STIMULATORY EFFECT OF ADENOSINE TRIPHOSPHATE AND MAGNESIUM ON THE RELEASE OF CATECHOLAMINES FROM ADRENAL MEDULLARY GRANULES

Abstract

The release of catecholamine from adrenal medullary granules which were incubated in 154 m[image] NaCl-5 m[image] KC1 solution was greatly stimulated by the addition of ATP together with Mg2+. Neither ATP nor Mg2+ alone had any effect on the release of catecholamine. Replacement of the medium containingl54 mMNaCl-5 m[image] KCl by 1 containing 154 m[image] KC1-5 m[image] NaCl did not affect the rate of ATP-MgZ+ stimulated catecholamine release. Ca2+, which by itself caused the release of catecholamine from the granules, was shown to be inhibitory in the presence of ATP and Mg2+. The molar of ATP to Mg2+ required for maximum release is thought to be about 21. The uptake of 14C-adrenaline [epinephrine] into the granules was also stimulated by ATP and Mg2+ under these conditions. The decrease of optical density at 520 mu in a granule suspension was accelerated by the addition of ATP and Mg2+. ATP and Mg2+ caused some structural changes in the granules, probably through the ATPase associated with the membranes of the granules, leading to the release of catecholamine from the granules.