Regulation of intracellular arachidonate in normal and stressed endothelial cells

The uptake of arachidonate and stearate from serum-free media by endothelial cells was investigated over a 48 h period. Arachidonate was rapidly incorporated into both the phospholipids and triacylglycerols. Triacylglycerol incorporation reached a maximum at 2 h and then rapidly declined with a concomitant increase in phospholipid incorporation. High initial arachidonate incorporation into phosphatidylcholine was followed by a partial transfer of that arachidonate to phosphatidylethanolamine. In contrast, stearate was slowly incorporated into all of the phospholipids and was not incorporated into the triacylglycerols. Cells stimulated with A23187 for 24 h cleaved stearate from all the phospholipids equally, whereas more arachidonate was cleaved from phosphatidylethanolamine than from the other phospholipids. Released arachidonate was both metabolized and reacylated into the triacylglycerols. Our results suggest that triacylglycerols serve as a modulator of intracellular arachidonate concentrations in endothelial cells.