title: Nitric oxide-20-hydroxyeicosatetraenoic acid interaction in the regulation of K+ channel activity and vascular tone in renal arterioles.
abstract: The present study examined whether inhibition of P4504A enzyme activity and the formation of 20-HETE contributes to the activation of K+ channels and vasodilator effects of nitric oxide (NO) in renal arterioles. Addition of an NO donor to the P4504A2 enzyme that produces 20-HETE increased visible light absorbance at 440 nm indicating that NO binds to heme in this enzyme. NO donors also dose-dependently inhibited the formation of 20-HETE in microsomes prepared from renal arterioles. In patch-clamp experiments, NO donors increased the open-state probability of a voltage-sensitive, large-conductance (195+/-9 pS) K+ channel recorded with cell-attached patches on renal arteriolar smooth muscle cells. Blockade of guanylyl cyclase with [1H-[1,2,4]Oxadiazolo[4,3-a] quinoxalin-1-one] (ODQ, 10 micromol/L), or cGMP-dependent kinase with 8R,9S,11S-(-)-9-methoxycarbamyl-8-methyl-2,3,9,10-tetrahydro-8, 11-epoxy-1H,8H,11H-2,7b,11a-trizadibenzo-(a,g)-cy-cloocta-(c ,d, e)-trinden-1-one (KT-5823) (1 micromol/L) did not alter the effects of NO on this channel. In contrast, inhibition of the formation of 20-HETE with 17-octadecynoic acid (1 micromol/L) activated this channel and masked the response to NO. Preventing the NO-induced reduction in intracellular 20-HETE levels also blocked the effects of NO on this channel. Sodium nitroprusside (SNP) increased the diameter of renal interlobular arteries preconstricted with phenylephrine to 80+/-4% of control. Blockade of guanylyl cyclase with ODQ (10 micromol/L) attenuated the response to SNP by 26+/-2%; however, fixing 20-HETE levels at 100 nmol/L reduced the response by 67+/-8%. Blockade of both pathways eliminated the response to SNP. These results indicate that inhibition of the formation of 20-HETE contributes to the activation of K+ channels and the vasodilator effects of NO in the renal microcirculation.
authors.affiliation: Department of Physiology and Cardiovascular Research Center, Medical College of Wisconsin, Milwaukee, WI, USA.
authors.forename: C W
authors.initials: CW
authors.lastname: Sun
authors.forename: M
authors.initials: M
authors.lastname: Alonso-Galicia
authors.forename: M R
authors.initials: MR
authors.lastname: Taheri
authors.forename: J R
authors.initials: JR
authors.lastname: Falck
authors.forename: D R
authors.initials: DR
authors.lastname: Harder
authors.forename: R J
authors.initials: RJ
authors.lastname: Roman
mesh_terms: D000818:Animals; D001160:Arterioles / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D003577:Cytochrome P-450 Enzyme System / Q000032:analysis; D004347:Drug Interactions; D006893:Hydroxyeicosatetraenoic Acids / Q000494:pharmacology*; D066298:In Vitro Techniques; D007313:Insecta / Q000166:cytology / Q000648:ultrastructure; D007668:Kidney / Q000098:blood supply* / Q000502:physiology; D008099:Liver / Q000648:ultrastructure; D008297:Male; D008861:Microsomes / Q000201:enzymology / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D009569:Nitric Oxide / Q000378:metabolism / Q000494:pharmacology*; D009599:Nitroprusside / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects* / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D006893:Hydroxyeicosatetraenoic Acids; D015221:Potassium Channels; D009599:Nitroprusside; D009569:Nitric Oxide; C055987:20-hydroxy-5,8,11,14-eicosatetraenoic acid; D003577:Cytochrome P-450 Enzyme System