ACTIVATION OF DIACYLGLYCEROL IN CULTURED ENDOTHELIAL-CELLS EXPOSED TOCYCLIC STRAIN

Confluent bovine aortic endothelial cells (EC) were grown on flexible membranes and subjected to 10% average strain at 60 cycles/min for up to 500 a. A biphasic increase in diacylglycerol (DAG) occurred, with a n initial transient peak at 10 s followed by sustained elevation to 50 0 s. The early peak corresponded to the transient formation of inosito l 1,4,5-trisphosphate, demonstrating hydrolysis of L-alpha-phosphatidy linositol (PI) by PI-specific phospholipase C. To determine the origin of the sustained DAG phase, we incubated confluent bovine aortic EC w ith I mu Ci/ml [C-14]myristate overnight and subjected them to cyclic strain. There was a decrease in phosphatidylcholine (PC) and a corresp onding increase in DAG at 10 s and 250 s: suggesting PC hydrolysis wit h the generation of DAG at both an early (10 s) and a late (250 s) pha se. [C-14]phosphatidylethanol, a specific product of phospholipase D ( PLD) in the presence of 1% ethanol, was measured in EC preincubated wi th [C-14]myristate. Cyclic strain led to an immediate and sustained ac tivation of PLD. Increased ethanol concentration led to a consistent d ecrease in DAG. Furthermore, when EC were pretreated with 1% ethanol, the strain-induced proliferative response was attenuated.