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

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Abstract
Adrenal medullary granules were isolated by millipore filtration and then lysed in deionized H2O. In a perfusion system the influence of concentration and pH was studied on the uptake of biogenic amines, (phenylethylamine, tyramine, dopamine, NA [noradrenaline, norepinephrine], A [adrenaline epinephrine], acetylcholine and histamine) and Na ions by lysed and by dialyzed material. The results suggest a 2-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 [maximum uptake] of 400-500 nmol/mg granules dry weight. This minor pool (pool 1) was fully charged at amine concentration > 10 mM. A larger pool binds selectively A and NA-possibly stereospecifically L-NA and L-A-with a Umax .apprx. 1500 nmol/mg granules. This larger pool (pool 2) required A and NA concentrations .apprx. 200-300 mM for maximal filling. In pool 2 CA+ [catecholamine] ions 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 (> 10-30 mM). ATP- ions become attached to the concomitantly unmasked +NH3 groups.