Extracellular Adenosine 5'-Triphosphate Decreases the Permeability of an Endothelial Cell Monolayer through Protein Kinase C.

Abstract

Adenosine 5′−triphosphate (ATP) is known to have various effects on cells as an extracellular nucleotide. It decreases the degree of edema and the requirement for intravenous hydration in critically ill patients. We examined the direct effects of ATP on the permeability of a vascular endothelial cell monolayer using an in vitro co−culture chamber system. Human umbilical vein endothelial cells were cultured on filter membranes of co−culture chambers to form a confluent monolayer. FITC-labeled 70k dalton dextran and ATP at various concentrations were added to the upper chamber. The concentrations of FITC−dextran, which permeated to the lower chamber through the endothelial cell monolayer, were determined in 4hr. A significant decrease in the permeability of FITC−dextran was observed with 10-6 to 10-3M of ATP. One, 10, 100, and 1000μM ATP decreased the permeability from 1.00±0.05 to 0.75±0.05, 0.66±0.04, 0.61±0.07, and 0.58±0.08 respectively (mean±SD, n=5, p<0.05). Adenosine, an ATP metabolite, did not change the permeability. Phorbol 12−myristate 13−acetate (PMA), a protein kinase C stimulator, decreased the permeability. Treatment with staurosporine, a protein kinase inhibitor, and myrystoylated protein kinase C (19-27), a protein kinase C specific inhibitor, suppressed the decrease of the permeability by ATP. These results indicated that ATP decreases the permeability of endothelial cell monolayers through protein kinase C (PKC) in a signal transduction system.