Nitric oxide-epoxygenase interactions and arachidonate-induced dilation of rat renal microvessels.
Nitric oxide (NO) is an inhibitor of hemoproteins including cytochrome P-450 enzymes. This study tested the hypothesis that NO inhibits cytochrome P-450 epoxygenase-dependent vascular responses in kidneys. In rat renal pressurized microvessels, arachidonic acid (AA, 0.03-1 microM) or bradykinin (BK, 0.1-3 microM) elicited NO- and prostanoid-independent vasodilation. Miconazole (1.5 microM) or 6-(2-propargyloxyphenyl)hexanoic acid (30 microM), both of which are inhibitors of epoxygenase enzymes, or the fixing of epoxide levels with 11,12-epoxyeicosatrienoic acid (11,12-EET; 1 and 3 microM) inhibited these responses. Apamin (1 microM), which is a large-conductance Ca2+-activated K+ (BKCa) channel inhibitor, or 18alpha-glycyrrhetinic acid (30 microM), which is an inhibitor of myoendothelial gap junctional electromechanical coupling, also inhibited these responses. NO donors spermine NONOate (1 and 3 microM) or sodium nitroprusside (0.3 and 3 microM) but not 8-bromo-cGMP (100 microM), which is an analog of cGMP (the second messenger of NO), blunted the dilation produced by AA or BK in a reversible manner without affecting that produced by hydralazine. However, the non-NO donor hydralazine did not affect the dilatory effect of AA or BK. Spermine NONOate did not affect the dilation produced by 11,12-EET, NS-1619 (a BKCa channel opener), or cromakalim (an ATP-sensitive K+ channel opener). AA and BK stimulated EET production, whereas hydralazine had no effect. On the other hand, spermine NONOate (3 microM) attenuated basal (19 +/- 7%; P < 0.05) and AA stimulation (1 microM, 29 +/- 9%; P < 0.05) of renal preglomerular vascular production of all regioisomeric EETs: 5,6-; 8,9-; 11,12-; and 14,15-EET. These results suggest that NO directly and reversibly inhibits epoxygenase-dependent dilation of rat renal microvessels without affecting the actions of epoxides on K+ channels.
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Center for Cardiovascular Diseases, College of Pharmacy and Health Sciences, Texas Southern University, 3100 Cleburne Street, Houston, TX 77004, USA.
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Oyekan
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D015126:8,11,14-Eicosatrienoic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D016718:Arachidonic Acid / Q000494:pharmacology*; D001920:Bradykinin / Q000494:pharmacology; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000494:pharmacology; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004852:Epoxy Compounds / Q000378:metabolism*; D017629:Gap Junctions / Q000502:physiology; D008297:Male; D008833:Microcirculation / Q000187:drug effects / Q000502:physiology; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009589:Nitrogen Oxides; D015221:Potassium Channels / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012079:Renal Circulation / Q000187:drug effects / Q000502:physiology*; D013096:Spermine / Q000031:analogs & derivatives* / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*; D014665:Vasodilator Agents / Q000494:pharmacology
D004852:Epoxy Compounds; D020030:Nitric Oxide Donors; D009589:Nitrogen Oxides; D015221:Potassium Channels; D014665:Vasodilator Agents; C091861:spermine nitric oxide complex; D016718:Arachidonic Acid; D013096:Spermine; C016276:8-bromocyclic GMP; D009569:Nitric Oxide; C046783:11,12-epoxy-5,8,14-eicosatrienoic acid; D003577:Cytochrome P-450 Enzyme System; D015126:8,11,14-Eicosatrienoic Acid; D006152:Cyclic GMP; D001920:Bradykinin