Lysis of chromaffin granules by phospholipase A2‐treated plasma membranes

Abstract

The possible involvement of phospholipase A₂ (PLA₂) in the release of catecholamines was examined in a cell-free model system, using isolated chromaffin granules and plasma membranes of adrenal medulla cells. Plasma membranes treated with PLA₂ in the presence of Ca²⁺ caused lysis of chromaffin granules which was also dependent on Ca²⁺. This finding suggests that Ca²⁺ acts in two steps of exocytosis, namely in the transformation of plasma membranes into a lytic form by PLA²⁺ and in the interaction of chromaffin granules with plasma membranes. These findings show good agreement with recently reported findings in leaky adrenal medulla cells, and suggest the involvement of PLA²⁺ in the release of catecholamines.