Activation of TxA2/PGH2 receptors and protein kinase C contribute to coronary dysfunction in superoxide treated rat hearts.
We have previously shown that superoxide anion (O2-) stimulates the release of vasoconstrictor prostanoids and induces a prolonged rise in coronary perfusion pressure (CPP) that persists even after removal of O2-. In this study, we tested the hypothesis that the increased CPP is mediated by activation of TxA2/ PGH2 (TP) receptors and protein kinase C (PKC)-dependent mechanisms. In Langendorff perfused rat hearts, O2- was applied for 15 min and then washed out over a period of 20 min. Application of O2- increased the release of vasoconstrictive (TxA2 and PGF2alpha) and decreased vasodilating (PGI2 and PGE2) prostanoids. Although indomethacin (10 microM), a cyclooxygenase inhibitor, attenuated the rise in CPP during O2- perfusion, the increase was not completely blocked. OKY 046Na (10 microM), a thromboxane synthase inhibitor, had no effect on O2--induced increases in CPP, whereas ONO 3708 (10 microM), a TP receptor antagonist, suppressed this effect. PKC activity was also elevated by more than 50% by O2- perfusion. CPP typically increased throughout the O2- wash-out. This post-O2- vasoconstriction was not inhibited by indomethacin, nitroglycerin or nitrendipine. In contrast, ONO 3708 (10 microM) and two PKC inhibitors, staurosporine (10 nM) and calphostin C (100 nM), completely blocked the rise in CPP, and even elicited vasodilation. PDBu enhanced the post-O2- vasoconstriction. We conclude that O2--induced coronary vasoconstriction is initially mediated by TP receptors, but activation of PKC sustains the response.
Gupte
S A
SA
Department of Physiology, Juntendo University School of Medicine, Tokyo, Japan. sagupte@med.juntendo.ac.jp
Okada
T
T
Tateyama
M
M
Ochi
R
R
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002317:Cardiovascular Agents / Q000494:pharmacology; D003327:Coronary Disease / Q000201:enzymology / Q000378:metabolism*; D015237:Dinoprost / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D008689:Methacrylates / Q000494:pharmacology; D009281:Naphthalenes / Q000494:pharmacology; D010477:Perfusion; D011453:Prostaglandins / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011982:Receptors, Prostaglandin / Q000378:metabolism*; D017482:Receptors, Thromboxane / Q000378:metabolism*; D044244:Receptors, Thromboxane A2, Prostaglandin H2; D019311:Staurosporine / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism*; D013928:Thromboxane A2 / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D013930:Thromboxane-A Synthase / Q000037:antagonists & inhibitors; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D002121:Calcium Channel Blockers; D002317:Cardiovascular Agents; D004791:Enzyme Inhibitors; D008689:Methacrylates; D009281:Naphthalenes; D011453:Prostaglandins; D011982:Receptors, Prostaglandin; D017482:Receptors, Thromboxane; D044244:Receptors, Thromboxane A2, Prostaglandin H2; D014662:Vasoconstrictor Agents; D013481:Superoxides; D013928:Thromboxane A2; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; C049855:ONO 3708; D015237:Dinoprost; D011493:Protein Kinase C; D013930:Thromboxane-A Synthase; D019311:Staurosporine; C058819:calphostin C; C034364:ozagrel; D007213:Indomethacin