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

Marie Pierre Junier, Fernand Dray, Ian Blair, Jorge Capdevila, Elizabeth Dishman, J. R. Falck, Sergio Ojeda

    Research output: Contribution to journalArticle

    54 Citations (Scopus)

    Abstract

    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 × 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.

    Original languageEnglish (US)
    Pages (from-to)1534-1540
    Number of pages7
    JournalEndocrinology
    Volume126
    Issue number3
    StatePublished - Mar 1990

    Fingerprint

    Median Eminence
    Dopamine D2 Receptors
    Somatostatin
    Hypothalamus
    Lipoxygenase
    Prostaglandin-Endoperoxide Synthases
    Gas Chromatography
    2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine
    Clotrimazole
    Ketoconazole
    Median Nerve
    Dopamine Agonists
    Neuropeptides
    Arachidonic Acid
    Cytochrome P-450 Enzyme System
    Esters
    High Pressure Liquid Chromatography
    Ions
    Neurons
    Acids

    ASJC Scopus subject areas

    • Endocrinology
    • Endocrinology, Diabetes and Metabolism

    Cite this

    Epoxygenase products of arachidonic acid are endogenous constituents of the hypothalamus involved in D2 receptor-mediated, dopamine-induced release of somatostatin. / Junier, Marie Pierre; Dray, Fernand; Blair, Ian; Capdevila, Jorge; Dishman, Elizabeth; Falck, J. R.; Ojeda, Sergio.

    In: Endocrinology, Vol. 126, No. 3, 03.1990, p. 1534-1540.

    Research output: Contribution to journalArticle

    Junier, Marie Pierre ; Dray, Fernand ; Blair, Ian ; Capdevila, Jorge ; Dishman, Elizabeth ; Falck, J. R. ; Ojeda, Sergio. / Epoxygenase products of arachidonic acid are endogenous constituents of the hypothalamus involved in D2 receptor-mediated, dopamine-induced release of somatostatin. In: Endocrinology. 1990 ; Vol. 126, No. 3. pp. 1534-1540.
    @article{6d56519f03ce4ece8b87a8bc76f663d1,
    title = "Epoxygenase products of arachidonic acid are endogenous constituents of the hypothalamus involved in D2 receptor-mediated, dopamine-induced release of somatostatin",
    abstract = "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 × 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.",
    author = "Junier, {Marie Pierre} and Fernand Dray and Ian Blair and Jorge Capdevila and Elizabeth Dishman and Falck, {J. R.} and Sergio Ojeda",
    year = "1990",
    month = "3",
    language = "English (US)",
    volume = "126",
    pages = "1534--1540",
    journal = "Endocrinology",
    issn = "0013-7227",
    publisher = "The Endocrine Society",
    number = "3",

    }

    TY - JOUR

    T1 - Epoxygenase products of arachidonic acid are endogenous constituents of the hypothalamus involved in D2 receptor-mediated, dopamine-induced release of somatostatin

    AU - Junier, Marie Pierre

    AU - Dray, Fernand

    AU - Blair, Ian

    AU - Capdevila, Jorge

    AU - Dishman, Elizabeth

    AU - Falck, J. R.

    AU - Ojeda, Sergio

    PY - 1990/3

    Y1 - 1990/3

    N2 - 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 × 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.

    AB - 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 × 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.

    UR - http://www.scopus.com/inward/record.url?scp=0025264864&partnerID=8YFLogxK

    UR - http://www.scopus.com/inward/citedby.url?scp=0025264864&partnerID=8YFLogxK

    M3 - Article

    C2 - 1968382

    AN - SCOPUS:0025264864

    VL - 126

    SP - 1534

    EP - 1540

    JO - Endocrinology

    JF - Endocrinology

    SN - 0013-7227

    IS - 3

    ER -