Action of protein kinase C in endothelin-induced contractions in rat aortic rings.
Endothelin (ET) is a potent vasoconstrictor peptide that induces characteristically long-lasting contractions. We used both intact and endothelium-denuded rat aortic rings to investigate the role of protein kinase C (PKC) in ET-induced contractions. ET (10(-9) M) and phorbol 12,13-dibutyrate (PDBu), a PKC activator, produced a gradual and sustained contraction of greater magnitude in denuded aortic rings than in intact rings. When aortic rings were pretreated with graded concentrations of different PKC inhibitors, inhibition of ET-induced contractions began at 10(-9)M and was nearly complete at 10(-3)M, and the reduction was greater in intact than in denuded rings. Pretreatment of aortic rings with PDBu or NG-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthase, potentiated ET-induced contractions. PKC enzyme assay showed activation of PKC in aortic rings that were treated with either ET or PDBu, inhibition after pretreatment with PKC inhibitors, and no change with 4 alpha-phorbol 12,13-didecanoate (PDD), an inactive phorbol ester. ET significantly increased nitrate and nitrite production, which was further increased by pretreatment with PKC inhibitors. PDBu prevented ET-induced nitrate/nitrite production, and PDD had no effect. These results strongly suggest that PKC mediates, in part, ET-induced contractions in rat aortic rings and that an intact endothelium is required for maximum inhibition by PKC inhibitors because PKC stimulated by ET inhibits nitric oxide release.
Oriji
G K
GK
Hypertension-Endocrine Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
Keiser
H R
HR
D000818:Animals; D001011:Aorta / Q000187:drug effects* / Q000201:enzymology / Q000502:physiology*; D016232:Endothelins / Q000494:pharmacology*; D004730:Endothelium, Vascular / Q000502:physiology; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009566:Nitrates / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology*
D016232:Endothelins; D004791:Enzyme Inhibitors; D009566:Nitrates; D009573:Nitrites; D015240:Phorbol 12,13-Dibutyrate; D011493:Protein Kinase C