In vitro studies on a cation dependent catecholamine release from a two-compartment storage in bovine adrenal...

Perfusion of adrenal medullary granules, isolated according to Poisner & Trifaró, with isotonic cation-containing solution (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 Umax of approximately 500 nmol/kg 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+ in equilibrium with CA+. The major compartment (pool 2) with a Umax of approximately 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 approximately 1500 nmol/mg matched the in vivo storage capacity for CA (approximately 1300 nmol/mg according to Hillarp 1960).