Role of extracellular arachidonate in regulation of prostaglandin biosynthesis in cultured 3T3 fibroblasts.

The stimuli that activate phospholipase releasing substrate fatty acids for PG biosynthesis also activates the reuptake of liberated fatty acids by the cell. The substrate released by these stimuli is accessible to albumin in 3T3 cells, and it is therefore presumably released into the extracellular space before it undergoes enzymatic conversion. Added exogenous arachidonate competes freely with endogenous arachidonate released by a stimulus, suggesting no apparent coupling mechanism between phospholipase and cyclooxygenase enzyme systems.