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J R Falck

Publications and source records attributed to J R Falck.

At least 217 records · Page 12Linked to original sources
PubMed1990

Metabolism of 12(S)-hydroxy-5,8,10,14-eicosatetraenoic acid and other hydroxylated fatty acids by the reductase pathway in porcine polymorphonuclear leukocytes.

We have previously shown that porcine polymorphonuclear leukocytes (PMNL) reduce leukotriene B4 (LTB4) to 10,11-dihydro-LTB4, 10,11-dihydro-12-epi-LTB4, and 10,11-dihydro-12-oxo-LTB4 [Wainwright et al. (1990) Biochemistry 29, 1180-1185]. We have now demonstrated that 12(S)-hydroxy-5,8,10,14-eicosatetraenoic acid [12(S)-HETE] is metabolized by a similar pathway in porcine PMNL. 12(S)-HETE was metabolized to two products that were identified by gas chromatography-mass spectrometry and nuclear magnetic resonance spectroscopy as 12-hydroxy-5,8,14-eicosatrienoic acid (10,11-dihydro-12-HETE) and 12-oxo-5,8,14-eicosatrienoic acid (10,11-dihydro-12-oxo-ETE). Derivatization of 12-hydroxy-5,8,14-eicosatrienoic acid with (R)-(+)-alpha-methoxy-alpha-(trifluoromethyl)phenylacetic acid, followed by chromatography on a silicic acid column, enabled the resolution of 12R and 12S stereoisomers, which were identified by cochromatography with synthetic standards. Incubation of 12(S)-HETE with PMNL for various times revealed that the stereochemistry of the 12-hydroxyl group of 12-hydroxy-5,8,14-eicosatrienoic acid was initially the same as that of 12(S)-HETE. However, after 40 min, 30% of the 12-hydroxy-5,8,14-eicosatrienoic acid had the opposite configuration at C12. 13-Hydroxy-9,11-octadecadienoic acid (13-HODE) was metabolized in a similar fashion by porcine PMNL to 13-hydroxy-9-octadecenoic acid (11,12-dihydro-13-HODE) and 13-oxooctadecenoic acid (11,12-dihydro-13-oxo-ODE). The apparent Km values for the reduction of 12-HETE, LTB4, and 13-HODE were 0.21, 0.28, and 2.22 microM, respectively. All three substrates had the same apparent Vmax [0.029 pmol min-1 (10(6) cells)-1]. Competition experiments between LTB4 and 12-HETE indicated that they were metabolized by the same pathway. Various structurally related compounds were metabolized by porcine PMNL in the order LTB4 = 6-trans-LTB4 greater than 12-epi-6-trans,8-cis-LTB4 greater than 12-epi-6-trans-LTB4 greater than 12-HETE greater than LTB5 greater than 15-HETE = 13-HODE much greater than 5-HETE greater than 9-HODE greater than 20-hydroxy-LTB4 greater than 12-hydroxy-5,8,10-heptadecatrienoic acid. Prostaglandins E2 and F2 alpha were not metabolized to any detectable products by porcine PMNL.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1990

Arachidonic acid epoxygenase. Stereochemical analysis of the endogenous epoxyeicosatrienoic acids of human kidney cortex.

Mass spectral and chromatographic analysis demonstrates the presence of 14,15-, 11,12- and 8,9-epoxyeicosatrienoic acids (44%, 33% and 23% of the total, respectively) in human kidney cortex. Chiral analysis of the human renal epoxyeicosatrienoic acids shows the formation of 8,9-, 11,12- and 14,15-epoxyeicosatrienoic acids in a 1:1, 4:1 and 2:1 ratio of antipodes, respectively. These results demonstrate the biosynthetic origin of the human kidney 11,12- and 14,15-epoxyeicosatrienoic acids and suggest a role for renal cytochrome P-450 in the bioactivation of endogenous pools of arachidonic acid.

8,11,14-Eicosatrienoic Acid↗
PubMed1990

Identification and biological activity of dihydroleukotriene B4: a prominent metabolite of leukotriene B4 in the human lung.

Exogenous [3H]leukotriene B4 (LTB4) was converted into several polar and non-polar metabolites in the chopped human lung. One of the major metabolites was identified as 5(S),12-dihydroxy-6,8,14-eicosatrienoic acid (10,11-dihydro-LTB4) by means of co-chromatography with authentic standards, ultraviolet spectrometry and gas chromatography-mass spectrometry. Analysis of chiral straight phase HPLC revealed the presence of both the 12(S) and 12(R) epimers of dihydro-LTB4. Dihydro-LTB4 was also formed from endogenously generated LTB4 in ionophore A23187 stimulated incubations. The dihydro metabolites were approximately 100 times less potent than LTB4 in causing guinea pig lung strip contraction and leukocyte-dependent inflammation in the hamster cheek pouch in vivo.

Animals↗
PubMed1990

Cytochrome P-450 enzyme-specific control of the regio- and enantiofacial selectivity of the microsomal arachidonic acid epoxygenase.

Chiral analysis of the rat liver microsomal arachidonic acid epoxygenase metabolites shows enantioselective formation of 8,9-, 11,12-, and 14,15-cis-epoxyeicosatrienoic acids in an approximately 2:1, 4:1, and 2:1 ratio of antipodes, respectively. Animal treatment with the cytochrome P-450 inducer phenobarbital increased the overall enantiofacial selectivity of the microsomal epoxygenase and caused a concomitant inversion in the absolute configurations of its metabolites. These effects of phenobarbital were time-dependent and temporally linked to increases in the concentration of microsomal cytochrome P-450 enzymes. Reconstitution of the epoxygenase reaction utilizing several purified cytochrome P-450 demonstrated that the asymmetry of epoxidation is under cytochrome P-450 enzyme control. These results established that the chirality of the hepatic arachidonic acid epoxygenase is under regulatory control and confirm cytochromes P-450 IIB1 and IIB2 as two of the endogenous epoxygenases induced in vivo by phenobarbital.

8,11,14-Eicosatrienoic Acid↗
PubMed1990

Cytochrome P-450-dependent oxidation of arachidonic acid to 16-, 17-, and 18-hydroxyeicosatetraenoic acids.

Incubation of rat liver microsomal fractions with arachidonic acid in the presence of NADPH results in the formation of three novel monohydroxylated fatty acid metabolites. Utilizing chromatographic and mass spectral techniques, these metabolites have been identified as 16-, 17-, and 18-hydroxyeicosatetraenoic acids. The NADPH-dependent microsomal metabolism of arachidonic acid to 16-, 17-, 18-, and 19-hydroxyeicosatetraenoic acids is induced after animal treatment with beta-naphthoflavone. Reconstitution of the arachidonic acid oxygenase utilizing individual purified cytochrome P-450 enzymes demonstrates regioselectivity, controlled by the protein catalyst, for the hydroxylation of the sp3 carbon atoms adjacent to the methyl end of the fatty acid.

Animals↗
PubMed1990

Effect of 14,15-epoxyeicosatrienoic acid infusion on blood pressure in normal and hypertensive rats.

Intravenous (IV) and intraarterial (IA) infusion of 14,15-epoxyeicosatrienoic acid (14,15-EET) produced a dose-dependent decrease in mean arterial blood pressure (MAP) in normal and spontaneously hypertensive rats (SHR). The hypotensive effect of 14,15-EET was observed from 1 microgram/kg to 10 micrograms/kg with a maximum reduction in MAP as much as 45 +/- 6 mmHg in both normal and SHR. In normal rats the hypotensive effect was found to be more pronounced when 14,15-EET was infused IA than IV. This suggests that 14,15-EET may be metabolized as it passes through the lungs. However, in SHR there was no difference in MAP when 14,15-EET was infused either IA or IV. This indicates that there is a differential removal of the epoxide across the pulmonary circulation. Administration of indomethacin failed to inhibit the hypotensive action of 14,15-EET, suggesting that it may not be a cyclo-oxygenase dependent mechanism. However, the PAF antagonist of BN-52021 inhibited the hypotensive action of 14,15-EET. This therefore, suggests that the release of PAF may be involved in the hypotensive action of this epoxide of arachidonic acid.

8,11,14-Eicosatrienoic Acid↗
PubMed1990

Stereochemistry of leukotriene B4 metabolites formed by the reductase pathway in porcine polymorphonuclear leukocytes: inversion of stereochemistry of the 12-hydroxyl group.

Leukotriene B4 (LTB4), a potent proinflammatory agent, is a major metabolite of arachidonic acid in polymorphonuclear leukocytes (PMNL). When porcine PMNL were incubated with LTB4 and the products purified by reversed-phase high-pressure liquid chromatography (HPLC), we previously identified two metabolites: 10,11-dihydro-LTB4 and 10,11-dihydro-12-oxo-LTB4 [Powell, W. S., & Gravelle, F. (1989) J. Biol. Chem. 264, 5364-5369]. Further analysis of the reaction products by normal-phase HPLC has now revealed the presence of a third major metabolite of LTB4. This product is not formed in detectable amounts in the first 5 min of the reaction but accounts for about 20-30% of the reaction products after 60 min, when LTB4 has been completely metabolized. The mass spectrum and gas chromatographic properties of the new metabolite are identical with those of 10,11-dihydro-LTB4, suggesting that it is a stereoisomer of this compound. This product was identified as 10,11-dihydro-12-epi-LTB4 [i.e., 5(S),12(R)-dihydroxy-6,8,14-eicosatrienoic acid] by comparison of its chromatographic properties with those of the authentic chemically synthesized compound. Both 10,11-dihydro-LTB4 and 10,11-dihydro-12-oxo-LTB4 were enzymatically converted to 10,11-dihydro-12-epi-LTB4 by porcine PMNL, the former compound being the better substrate. The reaction was reversible, since both 10,11-dihydro-12-epi-LTB4 and 10,11-dihydro-12-oxo-LTB4 could be converted to 10,11-dihydro-LTB4.(ABSTRACT TRUNCATED AT 250 WORDS)

Alcohol Oxidoreductases↗
PubMed1990

Cytochrome P450-dependent arachidonic acid metabolites, 19- and 20-hydroxyeicosatetraenoic acids, enhance sodium-potassium ATPase activity in vascular smooth muscle.

Several cytochrome P450-dependent arachidonic acid metabolites have been shown to affect Na+,K(+)-ATPase activity. In the present study, we tested the effect of omega- and omega - 1-hydroxylated products, i.e., 19- and 20-hydroxyeicosatetraenoic acids (19- and 20-HETE), on the K-induced relaxation in rat aortic rings. 19-HETE and 20-HETE increased the magnitude of the potassium-induced relaxation in a dose-dependent fashion (10(-7)-10(-5) M). The inhibitory effect of ouabain on the potassium-induced relaxation was reversed by both 19- and 20-HETE. In addition, indomethacin fully inhibited the stimulatory effect of 19- and 20-HETE on relaxation induced by potassium. Vascular ouabain-sensitive 86Rb uptake was also increased by 19- and 20-HETE. These observations suggest that 19- and 20-HETE stimulate vascular Na+,K(+)-ATPase via their conversion by cyclooxygenase to prostaglandin-like material.

Analysis of Variance↗
PubMed1990

Inhibition of renin release by 14,15-epoxyeicosatrienoic acid in renal cortical slices.

The effects of products of the cytochrome P-450 epoxygenase pathway of arachidonate metabolism on renin have not been previously examined. Initial high-performance liquid chromatography and gas chromatography-mass spectrometry studies documented the synthesis of four epoxyeicosatrienoic acid (EET) regioisomers of epoxygenase in superficial cortical slices from male Sprague-Dawley rats. Each regioisomer was tested for effects on both isoproterenol (ISO)-stimulated and basal renin secretion from cortical slices. ISO increased renin release significantly (169%, P less than 0.01) in all incubations; 14,15-EET (10(-6) M) significantly reduced this increase in stimulated renin release to 47%. The 5,6-, 8,9-, and 11,12-EETs did not significantly affect renin release. Basal renin release was not affected by any of the four EETs. To examine the mechanism of this inhibitory action, the effects of 14,15-EET on tissue adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 5'-cyclic monophosphate (cGMP) concentrations were measured. Tissue cAMP concentrations were sharply increased (4.75-fold, P less than 0.001) by ISO; 14,15-EET did not blunt this increase significantly. ISO and 14,15-EET did not affect tissue cGMP concentrations. Incubation of [14C]EET with cortical slices resulted in only 10% conversion of the 14,15-EET to 14,15-dihydroxyeicosatrienoic acid (DHET) (diol) after 90 min; no other metabolites were observed. The 14,15 DHET did not alter either basal or stimulated renin release. These studies document the synthesis of EETs in rat kidney and demonstrate a direct effect of the 14,15-EET to inhibit stimulated renin release. This inhibitory action occurs without an effect on tissue cAMP or cGMP concentrations.

8,11,14-Eicosatrienoic Acid↗
PubMed1990

Cytochrome P-450 arachidonate metabolites in rat kidney: characterization and hemodynamic responses.

Rat kidney cortical and medullary microsomal fractions catalyzed cytochrome P-450-linked metabolism of arachidonic acid (AA) to epoxyeicosatrienoic acids (EETs) (56 +/- 6% of total products in cortex and 10% in medulla) and 19- and 20-hydroxyeicosatetraenoic acids (19- and 20-OHAA) (36 +/- 4% in cortex and 90% in medulla). In addition, endogenous renal generation of EETs was established by negative ion-chemical ionization mass spectrometry. The total amount of EETs present in the rat kidney was approximately 1 microgram/g wet tissue. The responses to renal arterial administration of 20-OHAA and 5,6-EET were evaluated in anesthetized euvolemic rats. 20-OHAA resulted in ipsilateral dose-dependent natriuresis without affecting systemic or renal hemodynamics or glomerular filtration rate (GFR). Equimolar doses of 5,6-EET resulted in dose-dependent renal vasoconstriction and reduced GFR but were without effect on arterial pressure or sodium excretion. During cyclooxygenase inhibition, 5,6-EET caused renal vasodilatation and augmentation of GFR. These data establish the capacity of rat kidney to metabolize AA through cytochrome P-450-dependent oxygenases and demonstrate the endogenous formation of the resulting eicosanoids. Monooxygenase and epoxygenase products exert effects on renal blood flow, GFR, and urinary sodium excretion rate, suggesting their potential relevance in the regulation of renal function.

8,11,14-Eicosatrienoic Acid↗
PubMed1990

Synthesis of lipoxygenase and epoxygenase products of arachidonic acid by normal and stenosed canine coronary arteries.

Coronary vascular injury promotes blood cell-vessel wall interactions that influence arachidonic acid metabolism and coronary blood flow patterns. Since lipoxygenase and cytochrome P-450 epoxygenase metabolites of arachidonic acid are synthesized by vascular and inflammatory cells and have a variety of important biological actions, we investigated the metabolism of arachidonic acid by these pathways in normal and stenosed, endothelially injured canine coronary arteries. We found and confirmed by gas chromatography/mass spectrometry that primarily 12- and 15-hydroxyeicosatetraenoic acids (HETEs) are synthesized by both coronary artery segments. Lesser amounts of 11-, 9-, 8-, and 5-HETEs are also produced. 15-Ketoeicosatetraenoic acid is also synthesized. The synthesis of 14C-HETEs is fivefold to 10-fold greater by the stenosed than the normal coronary artery. Specific radioimmunoassays indicated that the stenosed coronary artery synthesized 93 +/- 14 and 1,102 +/- 154 ng/g of tissue of 15- and 12-HETE, respectively, while the normal coronary artery produced 17 +/- 3 and 162 +/- 68 ng/g of tissue of 15- and 12-HETE, respectively. Products comigrating with 14,15-; 11,12-; 8,9-; and 5,6-epoxyeicosatrienoic acids (EETs) and the corresponding dihydroxyeicosatrienoic acids (DHETs) were detected predominantly in stenosed coronary arteries by high-pressure liquid chromatography. The structures of the EETs were confirmed by GC/MS. The EETs and prostaglandin I2 produced endothelium-independent, concentration-related relaxations of dog coronary artery rings. These data indicate that normal and stenotic coronary arteries metabolize arachidonic acid to HETEs, DHETs, and EETs along with prostaglandins; however, the synthesis of these metabolites is greater in the stenosed, endothelially injured vessel. The EETs may be synthesized during the development of cyclic flow variations and counteract the vasoconstrictor effects of thromboxane A2.

8,11,14-Eicosatrienoic Acid↗
PubMed1990

5,6-epoxyeicosatrienoic acid, a novel arachidonate metabolite. Mechanism of vasoactivity in the rat.

We have reported that 5,6-epoxyeicosatrienoic acid (5,6-EET) was the only cytochrome P-450-dependent arachidonic acid (AA) epoxide to dilate the isolated, perfused caudal artery of the rat. We have investigated the mechanisms by which 5,6-EET dilates the rat-tail artery by studying the effect of deendothelialization and inhibition of AA metabolic pathways (cyclooxygenase, lipoxygenase, and cytochrome P-450 monooxygenase) on the vascular action of the epoxide. Rat isolated caudal arteries were perfused with Krebs-Henseleit solution at 37 degrees C, pH 7.4, and gassed with 95% O2-5% CO2. Arterial tone was elevated with phenylephrine; acetylcholine (0.5 nmol) was used to detect the presence of intact, functional endothelium. Doses of 5,6-EET, from 6.25 to 25.0 nmol, were injected close-arterially. After obtaining control responses, the same doses were randomly retested after deendothelialization or in the presence of inhibitors of AA metabolism. Removal of the endothelium decreased by 70% the vasodilator responses to 5,6-EET. The endothelial dependency was a function of the epoxide interacting with cyclooxygenase of the endothelium, because indomethacin (3 microM) and aspirin (50 microM) prevented the vasodilator response to 5,6-EET while not affecting the response to acetylcholine. SKF-525A (1.1 microM) and metyrapone (150 microM) did not affect the responses to the 5,6-EET, whereas clotrimazole (0.7 microM) and nordihydroguaiaretic acid (2.5 microM) had nonspecific effects, decreasing responses to 5,6-EET and acetylcholine. Because 5,6-EET failed to stimulate detectable release of prostanoids into the effluent from the caudal artery, we conclude that 5,6-EET requires conversion by cyclooxygenase for expression of its vasoactivity.

8,11,14-Eicosatrienoic Acid↗
PubMed1990

Epoxygenase products of arachidonic acid are endogenous constituents of the hypothalamus involved in D2 receptor-mediated, dopamine-induced release of somatostatin.

The epoxyeicosatrienoic acids (EETs) were discovered as products of a cyclooxygenase/lipoxygenase-independent, cytochrome P-450 catalyzed metabolism of arachidonic acid (AA) termed the "epoxygenase" pathway. The rat hypothalamus is able to synthesize EETs from exogenous AA, and 5,6-EET has been found to release the neuropeptide somatostatin (SRIF) from hypothalamic nerve terminals of the median eminence (ME). In the present study, hypothalami from male rats were examined for the presence of endogenous EETs, using chemical, chromatographic, and mass spectral analysis procedures. The samples were initially separated in a C18 Sepralyte column, fractionated on TLC plates, and purified by reverse phase HPLC. Thereafter, they were esterified (pentafluorobenzyl esters) and subjected to negative ion chemical ionization/gas chromatography (GC)/mass spectral (MS) analysis. The GC retention time and the MS fragmentation patterns revealed the presence of a mixture of 8,9-, 11,12- and 14,15-EETs; instability of 5,6-EET during the isolation protocol precluded its identification. Total hypothalamic EET concentration was estimated to be 120 ng/g wet tissue. The 8,9-regiosomer released SRIF from ME nerve terminals with an ED50 of 5 x 10(-12) M; Dopamine (DA) and the D2 receptor agonist PPHT, but not the D1 receptor agonist SKF-38393, induced SRIF release from the ME. This effect was blocked by clotrimazole and ketoconazole, two inhibitors of microsomal cytochrome P-450 function and AA epoxygenase in particular. In contrast, the inhibitors failed to affect the increase in SRIF release induced by 8,9-EET. These results indicate that: 1) in addition to cyclooxygenase and lipoxygenase products, epoxygenase metabolites of AA are endogenous compounds of the hypothalamus, and 2) EETs may mediate the increase in SRIF release from hypothalamic neurons induced by the interaction of DA with D2 receptors.

Animals↗
PubMed1989

Endogenous epoxyeicosatrienoic acids. Cytochrome P-450 controlled stereoselectivity of the hepatic arachidonic acid epoxygenase.

Chiral analysis of the endogenous rat liver epoxyeicosatrienoic acids shows the biosynthesis of 8,9-, 11,12-, and 14,15-epoxyeicosatrienoic acids in a 4:1, 2:1, and 3:1 ratio of antipodes, respectively. Animal treatment with phenobarbital results in a 3.7-fold increase in microsomal cytochrome P-450 concentration and a concomitant, regioselective 6.8- and 3.4-fold increase in the liver concentration of 8,9- and 14,15-epoxyeicosatrienoic acids, respectively. Phenobarbital induces the in vivo synthesis of both regioisomers as nearly optically pure enantiomers. These results demonstrate the enzymatic origin of the epoxyeicosatrienoic acids present in rat liver and document a novel metabolic function for cytochrome P-450 in the regio- and enatioselective epoxygenation of endogenous pools of arachidonic acid.

8,11,14-Eicosatrienoic Acid↗