In vitro studies on a two-pool stage of adrenaline and noradrenaline in granule material from bovine adrenal medulla.

Adrenal medullary granules were isolated by millipore filtration according to Poisner & Trifaró (1967) and then lysed in deionized water. In a perfusion system the influence of concentration of pH was studied on the uptake of biogenic amines (PhEA, TA, DA, NA, A, Arch and Hi) and sodium ions by lysed and by dialyzed material. The results suggest a two-pool storage of A and NA in the granules. A minor pool with cation exchanger properties binds unselectively organic (biogenic amines) and inorganic cations with a Umax of 400-500 nmol/mg granules dry-weight. This minor pool (pool 1) was fully charged at amine concentrations greater than 10 mM. A larger pool binds selectively A and NA--possibly stereospecifically L-NA and L-A--with a Umax approximately 1500 nmol/mg granules. This larger pool (pool 2) required A and NA concentrations approximately 200-300 mM for maximal filling. In pool 2 CA+ ions are assumed to be electrostatically linked to carboxyl groups, which become available as hypothetical COO----+H3N salt bridges are successively forced open by increasing CA concentrations (greater than 10-30 mM). ATP- ions become attached to the concomitantly unmasked +NH3 groups.