Epoxygenase metabolites contribute to nitric oxide-independent afferent arteriolar vasodilation in response to bradykinin.
In the kidney, epoxyeicosatrienoic acids (EETs) have been suggested to be endothelium-derived hyperpolarizing factors (EDHFs). The aim of the present study was to determine the contribution of EETs to the preglomerular vasodilation elicited by bradykinin. Sprague-Dawley rats were studied utilizing an in vitro perfused juxtamedullary nephron preparation. The afferent arteriolar diameter was determined and the diameter averaged 19 +/- 1 microm (n = 26) at a renal perfusion pressure of 100 mm Hg. Addition of 1, 10 and 100 nM bradykinin to the perfusate dose-dependently increased afferent arteriolar diameter by 5 +/- 1, 12 +/- 2 and 17 +/- 2%, respectively. The nitric oxide inhibitor N(omega)-nitro-L-arginine reduced bradykinin-induced afferent arteriolar vasodilation by 50%, and the diameter increased by 9 +/- 2% in response to 100 nM bradykinin. Epoxygenase inhibitors N-methylsulphonyl-6-(2-propargyloxyphenyl)hexanamide or miconazole greatly attenuated the nitric oxide-independent component of the vasodilation elicited by bradykinin. Cyclooxygenase (COX) inhibition attenuated the nitric oxide-independent vasodilation elicited by 1 nM bradykinin but did not significantly affect the vascular response to 100 nM bradykinin. Combined inhibition of nitric oxide, COX and epoxygenase pathways completely abolished bradykinin-mediated afferent arteriolar vasodilation. In additional studies, renal microvessels were isolated and incubated with bradykinin and samples were analyzed by NICI/GC/MS. Under control conditions, renal microvascular EET levels averaged 49 +/- 9 pg/mg/20 min (n = 7). In the presence of bradykinin, EET levels were significantly higher and averaged 81 +/- 11 pg/mg/20 min (n = 7). These data support the concept that EETs are EDHFs and contribute to the nitric oxide-independent afferent arteriolar vasodilation elicited by bradykinin.
Imig
J D
JD
Department of Physiology, Tulane University School of Medicine, New Orleans, La., USA.
Falck
J R
JR
Wei
S
S
Capdevila
J H
JH
D015126:8,11,14-Eicosatrienoic Acid / Q000097:blood; D000577:Amides / Q000494:pharmacology; D000818:Animals; D001160:Arterioles / Q000187:drug effects / Q000502:physiology*; D001920:Bradykinin / Q000494:pharmacology*; D046508:Culture Techniques; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D000090762:Cytochrome P-450 CYP2J2; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007213:Indomethacin / Q000494:pharmacology; D007668:Kidney / Q000098:blood supply* / Q000201:enzymology; D007700:Kinetics; D008297:Male; D008833:Microcirculation / Q000187:drug effects; D009569:Nitric Oxide / Q000502:physiology*; D019335:Nitroarginine / Q000494:pharmacology; D010105:Oxygenases / Q000037:antagonists & inhibitors / Q000502:physiology*; D011451:Prostaglandin-Endoperoxide Synthases / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012079:Renal Circulation / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects*
D000577:Amides; D016861:Cyclooxygenase Inhibitors; D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; C121756:N-methylsulfonyl-6-(2-propargyloxyphenyl)hexanamide; D019335:Nitroarginine; D009569:Nitric Oxide; D003577:Cytochrome P-450 Enzyme System; D010105:Oxygenases; D000090762:Cytochrome P-450 CYP2J2; D011451:Prostaglandin-Endoperoxide Synthases; D015126:8,11,14-Eicosatrienoic Acid; D001920:Bradykinin; D007213:Indomethacin