title: Stimulation of metamorphosis in Hydractinia echinata involves generation of lysophosphatidylcholine.
abstract: Whilst the significance of the phosphoinositide cycle in the activation of developmental events by extra-cellular signals is well established, the involvement of the phosphatidylcholine (PC) cycle is a matter just emerging. In the present study, the metabolism of phosphatidylcholine in early metamorphosis of Hydractinia echinata (Coelenterata; Hydrozoa) was investigated by incubation of planula larvae with3H-choline, extraction of the metabolites and isolation of the metabolites by thin-layer chromatography (TLC). Phosphatidylcholine (PC), lysophosphatidylcholine (LPC), acetylcholine and glycerophosphocholine were the labelled metabolites. Induction of metamorphosis did not stimulate an increased incorporation of choline into PC. In larvae preincubated with3H-choline to a steady state level of incorporation, a significant transient elevation of the radioactive label in LPC was observed 90 min after addition of metamorphosis stimulating agents. LPC probably derived from PC by the action of a phospholipase A2(PLA2). LPCs from bovine and soybean origin as well as isolated larval LPC did not influence metamorphosis. PLA2from bee venom promoted Cs+-induced metamorphosis but did not influence phorbol ester-induced metamorphosis. The data suggest that a PLA2is activated during metamorphosis. This PLA2activation does not occur in those putative receptor cells which receive the primary external inducing stimulus but in the many larval cells which resume proliferation or differentiation in response to a second, internally propagated signal.
authors.affiliation: Zoologisches Institut der Universität, Im Neuenheimer Feld 230, W-6900, Heidelberg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Leitz
authors.affiliation: Zoologisches Institut der Universität, Im Neuenheimer Feld 230, W-6900, Heidelberg, Germany.
authors.forename: Urte
authors.initials: U
authors.lastname: Müller
keywords: Hydractinia echinata; Hydrozoa; Lysophosphatidylcholine; Metamorphosis; Phospholipase A2