Ceramide induces resumption of meiosis in Bufo arenarum oocytes

BUSCHIAZZO J.; ALONSO T. S.; BONINI I. C.

Villa Carlos Paz, Cordoba

Congreso; XLIV Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB); 2008

SOCIEDAD ARGENTINA DE INVESTIGACION EN BIOQUIMICA Y BIOLOGIA MOLECULAR

Ceramides are generated in response to cellular stimulation by progesterone in amphibian oocytes. In this work, ceramide is analyzed for its ability to induce germinal vesicle breakdown (GVBD) indicative of maturation. Methyl-B-cyclodextrin (MBCD) was used for cellular cholesterol modulation in order to assess membrane raft involvement. Oocytes arrested in meiosis I were incubated for 24 h in a saline solution with C2-ceramide or the corresponding dihydroceramide solubilized in dimethylsufoxide (DMSO) at different concentrations.  Progesterone-induced maturation was achieved by incubation of oocytes with the steroid for 24 h. To remove cellular cholesterol, oocytes were pretreated with 25mM MBCD and subjected to incubation with either progesterone or ceramide. A detergent-free protocol was used to isolate caveolae-like membranes. Treatment of oocytes with exogenous C2-ceramide induced GVBD without evidence of cytotoxicity at 100 µg/ml concentration with a maximal response at 150 µg/ml. C2-dihydroceramide and DMSO induced no GVBD at the concentrations assayed. When MBCD-treated oocytes were incubated with ceramide, maturation was significantly inhibited. In contrast to progesterone, ceramide incubation affected the distribution caveolin and c-Src among membrane fractions. Results suggest that ceramide induces maturation probably by a pathway different from that of the steroid hormone.