In vitro studies on a cation dependent catecholamine release from a two‐compartment storage in bovine adrenal medullary granules

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Abstract
Perfusion of adrenal medullary granules, isolated according to Poisner & Trifaró, with isotonic cation‐containing solutions (NaCl, KCl, LiCl) caused a concentration dependent release of CA. The course of the release indicated the existence of a two‐compartment storage of CA. The minor compartment (pool 1) with a Umaxof ˜500 nmol/mg granule dry weight showed the characteristics of a cation exchanger and was assumed to be depleted on exposure to cations, e.g. sodium ions, as an ion exchange Na‐← CA+. The major compartment (pool 2) with a Umaxof ˜1000 nmol/mg stored both CA and ATP. It was assumed to empty via the cation exchanger pool. The total storage capacity of the two compartments ˜1500 nmol/mg matched the in vivo storage capacity for CA (˜1300 nmol/mg according to Hillarp 1960).