Adenosine Triphosphate Stimulates Inositol Phospholipid Metabolism and Prostacyclin Formation in Adrenal Medullary Endothelial Cells by Means of P2-purinergic Receptors

In the adrenal medulla, chromaffin cells secrete high concentrations of catecholamines, ATP, peptides and other factors that must pass through an endothelial cell barrier to enter the bloodstream. We have measured the effect of several of these chromaffin cell secretory products on cultured bovine adrenal medullary endothelial cells and have found that only ATP stimulates prostacyclin formation. The stimulation of prostacyclin formation by ATP coincides with the metabolism of inositol phospholipids and the accumulation of the putative second messenger inositol trisphosphate. The time course, concentration dependence, and P2-purinergic receptor specificity were similar for ATP-stimulated prostacyclin formation and ATP-stimulated inositol phospholipid metabolism. Thus, the increase in prostacyclin formation may be secondary to mobilization of intracellular Ca2+ by inositol trisphosphate, leading to activation of phospholipase A2, liberation of arachidonic acid, and the conversion of arachidonic acid to prostacyclin. We propose that the function of ATP, which is often colocalized with cell-specific hormones in secretory cells, may be to regulate blood flow in the adrenal medulla and other endocrine tissues by interacting with adjacent endothelial cells.