EFFECTS OF OXYGEN-TENSION AND SHEAR-STRESS ON HUMAN ENDOTHELIAL-CELL PROSTACYCLIN PRODUCTION

Under in vivo conditions of ischemia and reperfusion, vascular endothe lium (EC) experience concurrent changes in oxygen tension, shear stres s, and the local concentration of metabolites. These studies explored the combined effects of shear stress and oxygen tension on EC prostacy clin production. EC grown on microcarrier beads were exposed to 120 mi n of normoxia and basal shear stress by stirring at 20 rpm. After norm oxia, EC were exposed to hypoxia (2% O-2, 20 rpm), ischemia (2% O-2, 5 rpm) or sham ischemia (20% O-2, 5 rpm). Following hypoxia, EC were re oxygenated (20% O-2, 20 rpm). After ischemia and sham ischemia, EC wer e reperfused (20% O-2, 20 rpm). Minimal accumulation of metabolites oc curred during normoxia, hypoxia, and reperfusion. All metabolites were allowed to accumulate in the flasks during ischemia and sham ischemia . Prostacyclin levels were measured by ELISA, and prostaglandin H-2 sy nthase levels in cells were analyzed by immunoblotting. An acute decre ase in shear stress decreased prostacyclin production. An acute decrea se only in oxygen tension did not alter prostacyclin production signif icantly. The combined acute decrease in both shear stress and oxygen t ension significantly stimulated prostacyclin production for 30 min. By 120 min of ischemia and hypoxia, prostacyclin release was significant ly less than sham ischemia. Prostacyclin production after 30 min of re oxygenation was significantly less than that of cells subjected to rep erfusion. By 120 min of reperfusion and reoxygenation, there was no si gnificant difference in EC prostacyclin synthesis. These findings sugg est that temporal and quantitative aspects of EC prostaglandin synthes is are dependent on both oxygen tension and shear stress. (C) 1997 Aca demic Press.