Formation and biological activity of 12-ketoeicosatetraenoic acid in the nervous system of Aplysia.
12-Hydroperoxy-5,8,10,14-eicosatetraenoic acid (12-HPETE), a lipoxygenase product, simulates the synaptic responses produced by the modulatory transmitter, histamine, and the neuroactive peptide, Phe-Met-Arg-Phe-amide (FMRFamide), in identified neurons of the marine mollusk, Aplysia californica (Piomelli, D., Shapiro, E., Feinmark, S. J., and Schwartz, J. H. (1987) J. Neurosci. 7, 3675-3886; Shapiro, E., Piomelli, D., Feinmark, S., Vogel, S., Chin, G., and Schwartz, J. H. (1988) Cold Spring Harbor Symp. Quant. Biol. 53, in press). The 12-lipoxygenase pathway has not yet been fully characterized, but 12-HPETE is known to be metabolized further. We therefore began to search for other metabolites in order to investigate whether the actions of 12-HPETE might require its conversion to other active products. Here we report the identification of 12-keto-5,8,10,14-eicosatetraenoic acid (12-KETE), a metabolite of 12-HPETE formed by Aplysia nervous tissue. This product was identified in incubations of the tissue with arachidonic acid using high performance liquid chromatography, UV spectrometry, and gas chromatography/mass spectrometry. [3H]12-KETE was formed from endogenous lipid stores in nervous tissue, labeled by incubation with [3H]arachidonic acid, when stimulated by application of histamine. In L14 and L10 cells, identified neurons in the abdominal ganglion, applications of 12-KETE elicit changes in membrane potential similar to those evoked by histamine. 12(S)-Hydroxy-5,8,10,14-eicosatetraenoic acid, another metabolite of 12-HPETE, is inactive. These results support the hypothesis that 12-HPETE and its metabolite, 12-KETE, participate in transduction of histamine responses in Aplysia neurons.
Piomelli
D
D
Howard Hughes Medical Institute, Center for Neurobiology and Behavior, Columbia University, New York, New York 10032.
Feinmark
S J
SJ
Shapiro
E
E
Schwartz
J H
JH
D000818:Animals; D001048:Aplysia / Q000378:metabolism*; D001092:Arachidonate 12-Lipoxygenase / Q000378:metabolism; D001095:Arachidonic Acids / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D008401:Gas Chromatography-Mass Spectrometry; D006632:Histamine / Q000494:pharmacology; D015289:Leukotrienes / Q000378:metabolism*
C054994:12-keto-5,8,11,13-eicosatetraenoic acid; D001095:Arachidonic Acids; D015289:Leukotrienes; C021201:12-HPETE; D006632:Histamine; D001092:Arachidonate 12-Lipoxygenase