The vasoactive peptide, endothelin-1 (ET-1) has been implicated in the pathophysiology of various disease that are accompanied by disturbances in the regulation of vascular tone. Recently, we have shown that human brain endothelial cells secrete both immunoreactive ET-1 and express high-affinity ET-A receptors coupled to activation of phospholipase C (PLC). The present study demonstrates a dose-dependent stimulation of prostaglandins [thromboxane B2 (TxB2), prostaglandins F2alpha (PGF2alpha), 6-keto prostaglandin F1alpha (6-keto PGF1alpha), prostaglandin E2 (PGE2), and prostaglandin D2 (PGD2) production by ET-1 in capillary endothelial cells derived from human brain (HBEC). Prostaglandin formation (with the exception of PGD2) was blocked by both dexamethasone (50 micromoles) and neomycin (50 micromoles). The increase in the vasoconstrictive prostaglandins TxB2 and PGF2alpha temporally precede that of the vasodilatory 6-keto PGF1alpha, PGE2, and PGD2 and was already seen after 15 min of incubation with ET-1 (10 nM). Increased production of vasodilatory prostaglandins was observed between 4-8 hr of incubation, whereas normalization of both vasoconstrictive and vasodilatory prostaglandins occurred 24 hr after addition of ET-1. In contrast, endothelin -3(ET-3) had no effect on prostanoids production by HBEC. ET-1-stimulated prostaglandin secretion by HBEC was diminished by verapamil (10 micromoles) suggesting that activation of phospholipase A2 (PLA2) by ET-1 was partly induced by extracellular calcium influx. Data indicate that ET-1 activates PLA2 both directly and indirectly though PLC activation, and subsequently induces formation of vasoactive prostanoids that might contribute to the vasoactive actions of ET-1 both qualitatively and quantitatively. The detected response of the various prostanoids to ET-1 in the HBEC strongly suggest that the endothelium can play a significant role in the reactivities of the capillaries (dilatation, constriction, permeability) under normal and pathologic conditions.
