. Effect of Dehydroleucodine on meiosis reinitiation in Bufo arenarum denuded oocytes

SÁNCHEZ-TORANZO G., GIORDANO O.S., LOPEZ L.A. BUHLER M.I.

ZYGOTE

Cambridge University Press

Lugar: Cambridge, UK; Año: 2007 vol. 15 p. 183 - 187

In amphibian oocytes meiosis, the transition from G2 to M phase is regulated by the maturation promoting factor (MPF), a complex of the cyclin dependent kinase p34/cdc2 and cyclin B. In immature oocytes there is an inactive complex (pre-MPF), where cdc2 is phosphorylated on both Thr-161 and Thr-14/Tyr-15 residues. The dephosphorylation of Thr-14/Tyr-15 is necessary for the start of MPF activation and it is induced by the activation of Cdc 25 phosphatase. Late, to complete the activation, a small amount of active MPF induces an auto-amplification loop of MPF stimulation (MPF amplification). Dehydroleucodine (DhL) is a sesquiterpenic lactone that inhibits mammalian cell proliferation in G2. We asked whether DhL interferes with MPF activation. For this propose, the effect of DhL (up to 30 ìM) was evaluated on the resumption of meiosis, visualized by germinal vesicle break down (GVBD), of Bufo arenarum oocytes induced in vitro by a) removing follicle cells, b) progesterone stimulation, c) VG-content injection and d) injection of mature cytoplasm. The results show that DhL induced GVBD inhibition, in a dose-dependent manner, in spontaneous and progesterone-induced oocyte maturation. Nevertheless, DhL at the doses assayed had no effect on GVBD induced by mature cytoplasm injection but exerted an inhibitory effect on GVBD induced by GV-content. On the basis of this results, we interpreted that DhL does not inhibit MPF amplification and that the target of DhL is any event in the early stages of the Cdc 25 activation cascade. .