Possible involvement of arachidonic acid and eicosanoids in metamorphic events in Hydractinia echinata (Coelenterata; Hydrozoa)
Leitz, T.; Beck, H.; Stephan, M.; Lehmann, W.D.; De Petrocellis, L.; Di Marzo, V.
Journal of Experimental Zoology 269(5): 422-431
ISSN/ISBN: 0022-104X PMID: 8057074 DOI: 10.1002/jez.1402690505
Upon induction of metamorphosis, larvae of the marine hydroid Hydractinia echinata release (14C)-arachidonic acid from previously labeled endogenous sources. The lipoxygenase inhibitors nordihydroguaiaretic acid and 5,8,11,14-eicosatetraynoic acid inhibited metamorphosis induced by Cs+ and 1,2-sn-dioctanoylglycerol, whereas the inhibitors of cyclooxygenase, indomethacin, and acetylsalicylic acid were ineffective, suggesting a role for lipoxygenase metabolites of arachidonic acid in induction of metamorphosis. Lipoxygenase products in Hydractinia echinata were isolated and identified by gas chromatography/mass spectrometry. 8- and 12-HETE were the most abundant metabolites. In cytosolic fractions from larvae activity of an arachidonic acid metabolizing enzyme, presumably a lipoxygenase, was found. The metabolic product was identified by 1H-NMR and chiral phase HPLC as 8(R)-HETE. Its production was strongly inhibited by NDGA, but not by indomethacin.