title: Cytochrome P-450 arachidonic acid epoxygenase. Regulatory control of the renal epoxygenase by dietary salt loading.
abstract: The rat kidney microsomal epoxygenase catalyzed the asymmetric epoxidation of arachidonic acid to generate as major products: 8(R),9(S)-, 11(R),12(S)- and 14(S),15(R)-epoxyeicosatrienoic acids with optical purities of 97, 88, and 70%, respectively. Inhibition studies utilizing a panel of polyclonal antibodies to several rat liver cytochrome P-450 isoforms, indicated that the renal epoxygenase(s) belongs to the cytochrome P-450 2C gene family. Dietary salt, administered either as a 2-2.5% (w/v) solution in the drinking water or as a modified solid diet containing 8% NaCl (w/w), resulted in marked and selective increases in the renal microsomal epoxygenase activity (416 and 260% of controls, for the liquid and solid forms of NaCl, respectively) with no significant changes in the microsomal omega/omega-1 oxygenase or in the hepatic arachidonic acid monooxygenase reaction. Immunoblotting studies demonstrated that dietary salt induced marked increases in the concentration of a cytochrome P-450 isoform(s) recognized by polyclonal antibodies raised against human liver cytochrome P-450 2C10 or rat liver cytochrome P-450 2C11. Comparisons of the stereochemical selectivity of the induced and non-induced microsomal epoxygenase(s) with that of purified rat liver cytochrome P-450 2C11 suggest that the salt-induced protein(s) is catalytically and structurally different from liver cytochrome P-450 2C11. The in vivo significance of dietary salt in regulating the activities of the kidney endogenous arachidonic acid epoxygenase was established by the demonstration of a salt-induced 10-20-fold increase in the urinary output of epoxygenase metabolites. These results, in conjunction with published evidence demonstrating the potent biological activities of its metabolites, suggest a role for the epoxygenase in the renal response to dietary salt.
authors.affiliation: Division of Nephrology, Vanderbilt University Medical School, Nashville, Tennessee 37232.
authors.forename: J H
authors.initials: JH
authors.lastname: Capdevila
authors.forename: S
authors.initials: S
authors.lastname: Wei
authors.forename: J
authors.initials: J
authors.lastname: Yan
authors.forename: A
authors.initials: A
authors.lastname: Karara
authors.forename: H R
authors.initials: HR
authors.lastname: Jacobson
authors.forename: J R
authors.initials: JR
authors.lastname: Falck
authors.forename: F P
authors.initials: FP
authors.lastname: Guengerich
authors.forename: R N
authors.initials: RN
authors.lastname: DuBois
mesh_terms: D015126:8,11,14-Eicosatrienoic Acid / Q000652:urine; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D000090762:Cytochrome P-450 CYP2J2; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D004032:Diet; D008401:Gas Chromatography-Mass Spectrometry; D006893:Hydroxyeicosatetraenoic Acids / Q000652:urine; D007122:Immunoelectrophoresis; D007668:Kidney / Q000201:enzymology*; D008297:Male; D013058:Mass Spectrometry; D008861:Microsomes / Q000201:enzymology; D005810:Multigene Family; D010105:Oxygenases / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012965:Sodium Chloride / Q000494:pharmacology*
chemical_list: D006893:Hydroxyeicosatetraenoic Acids; D012965:Sodium Chloride; D003577:Cytochrome P-450 Enzyme System; D010105:Oxygenases; D000090762:Cytochrome P-450 CYP2J2; D015126:8,11,14-Eicosatrienoic Acid