Activation of phospholipase D by endothelin-1 and other pharmacological agents in rabbit iris sphincter smooth muscle.
The stimulation of phospholipase D (PLD) activity by endothelin-1 (ET1) was investigated in rabbit iris sphincter prelabelled with [3H]myristic acid. In the presence of 0.5% ethanol, ET1 caused a time- and dose-dependent increase in the production of [3H]phosphatidylethanol ([3H]PEt). Within 30 s the peptide increased PEt formation by 30% and after 5 min increased it by 140%. The EC50 value for ET1-stimulated PEt formation was found to be 30 nM. This value is appreciably lower than the EC50 we previously obtained for ET1-induced inositol trisphosphate production (45 nM), but considerably higher than that for arachidonic acid release (1 nM). PEt formation was significantly stimulated by prostaglandin F20, phorbol 12,13-dibutyrate (PDBu), chloroform, A23187 and A1F4-, but it was not affected by carbachol or the platelet-activating factor. PDBu-stimulated PEt formation was blocked by staurosporine and it was not potentiated by A23187. Staurosporine had no effect on ET1-stimulated PEt formation. Our data indicate that ET1 stimulation of PLD occurs independently of protein kinase C activation, phospholipase C activation and intracellular Ca2+ mobilization, and phospholipase A2 activation. In this tissue the ET1 receptor is probably coupled to the three phospholipases through several G-proteins, and this appears to be species and receptor type specific.
Zhang
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Y
Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta 30912-2100.
Abdel-Latif
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AA
D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D016232:Endothelins / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D019204:GTP-Binding Proteins / Q000378:metabolism; D066298:In Vitro Techniques; D007498:Iris / Q000187:drug effects / Q000201:enzymology*; D007700:Kinetics; D009130:Muscle, Smooth / Q000187:drug effects / Q000201:enzymology; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D010739:Phospholipase D / Q000378:metabolism*; D010743:Phospholipids / Q000096:biosynthesis; D011817:Rabbits; D017466:Receptors, Endothelin / Q000378:metabolism; D015398:Signal Transduction; D019311:Staurosporine; D010738:Type C Phospholipases / Q000378:metabolism
D000470:Alkaloids; D016232:Endothelins; D010743:Phospholipids; D017466:Receptors, Endothelin; D015240:Phorbol 12,13-Dibutyrate; D010738:Type C Phospholipases; D010739:Phospholipase D; D019204:GTP-Binding Proteins; D019311:Staurosporine