Catecholamine transport through a lipid barrier

Abstract

NORADRENALINE and adrenaline are stored in relatively high concentration together with nucleotides (mainly adenosine-5′-triphosphate (ATP)), bivalent cations (for example Ca²⁺ and Mg²⁺) and water-soluble proteins, in special intracellular organelles such as chromaffin granules of adrenal medulla¹. In the uptake of catecholamines by these organelles a specific mechanism is probably involved at the level of the granular membrane². Furthermore, formation of low molecular weight complexes between catecholamines and ATP^3,4 and mixed amine–nucleotide aggregates of apparent high molecular weight^5–8 has been demonstrated. The present experiments deal with the role of these interactions for the uptake and storage of the amines. Evidence will be presented that an ‘uphill’ transport of neurotransmitters occurs if ATP is present on on one side of an artificial lipid barrier and that this effect is connected with a reduction in the osmotic pressure of the biogenic monoamines by ATP.