Extracellular adenosine 5 '-triphosphate decreases the permeability of an endothelial cell monolayer through protein kinase C

Adenosine 5'-triphosphate (ATP) is known to have Various effects on cells a s an extracellular nucleotide, It decreases the degree of edema and the req uirement for intravenous hydration in critically ill patients. We examined the direct effects of ATP on the permeability of a vascular endothelial cel l monolayer using an in vitro co-culture chamber system. Human umbilical vein endothelial cells were cultured on filter membranes of cc-culture chambers to form a confluent monolayer. FITC-labeled 70 k dalto n dextran and ATP at various concentrations were added to the upper chamber . The concentrations of FITC-dextran, which chamber through me endothelial cell monolayer, were determined in 4 hr. A significant decrease in the perm eability of FITC-dextran was observed with 10(-6) to 10(-3) M of ATP. One, 10, 100,and 1000 mu M 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 permeabi lity. 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 sys tem.