ATP is stored in lamellar bodies to activate vesicular P2X in an autocrine fashion upon exocytosis.

Vesicular P2X receptors are known to facilitate secretion and activation of pulmonary surfactant in the alveoli of the lungs. P2X receptors are expressed in the membrane of lamellar bodies (LBs), large secretory lysosomes that store lung surfactant in alveolar type II epithelial cells, and become inserted into the plasma membrane after exocytosis. Subsequent activation of P2X receptors by adenosine triphosphate (ATP) results in local fusion-activated cation entry (FACE), facilitating fusion pore dilation, surfactant secretion, and surfactant activation.