Thrombin and histamine activate phospholipase C in human endothelial cells via a phorbol ester-sensitive pathway.
The effects of phorbol esters and synthetic diglycerides on thrombin- and histamine-stimulated increases in inositol trisphosphate (IP3) and cytosolic free calcium [( Ca2+]i) were studied in cultured human umbilical vein endothelial cells (HEC). Thrombin (0.003-3.0 U/ml) and histamine (10(-7)-10(-4) M) induced rapid increases in [Ca2+]i in suspended cells as monitored with the fluorescent calcium indicator fura-2. In [3H]myoinositol-labeled cells, both thrombin (3 U/ml)- and histamine (10(-4) M)-induced IP3 increases (195% +/- 6% and 98% +/- 4%, respectively) occurred in less than 15 sec and were temporally correlated with [Ca2+]i increases. Brief incubations (5-60 min) with different protein kinase C activators [4-beta-phorbol 12-myristate 13-acetate (1-100 nM), mezerein (100 nM), and sn-1,2 dioctanoylglycerol (0.1-10 microM)] attenuated agonist-induced increases in [Ca2+]i. These compounds also inhibited thrombin- and histamine-stimulated IP3 formation, thus suggesting a tight coupling between phospholipase C activation and calcium flux in cultured HEC. Overall, these observations suggest that the pathway linking receptors to phospholipase C stimulation in human endothelial cells is sensitive to protein kinase C activation.
Brock
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TA
Department of Pathology, Brigham and Women's Hospital, Boston, Massachusetts.
Capasso
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EA
D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D004789:Enzyme Activation; D006632:Histamine / Q000494:pharmacology*; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000378:metabolism; D010703:Phorbol Esters / Q000494:pharmacology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013917:Thrombin / Q000494:pharmacology*; D010738:Type C Phospholipases / Q000378:metabolism*
D007295:Inositol Phosphates; D010703:Phorbol Esters; D006632:Histamine; D015544:Inositol 1,4,5-Trisphosphate; D010738:Type C Phospholipases; D013917:Thrombin; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium