Sperm capacitation: Structural changes in membrane microdomains (RAFT)

BOARELLI PV; MONCLUS MA; DE ROSAS JC; VINCENTI AE; FORNÉS MW

Merlo, San Luis

Congreso; Reunión Conjunta de: XXII Reunión Científica Anual de la Sociedad de Biología de Cuyo y II Reunión Científica de la Sociedad Argentina de Microscopía (SAMIC); 2004

Sociedad de Biología de Cuyo

Membrane microdomains containing cholesterol and sphingolipids conform structures with specific functions in sperm (e.g. cholesterol lost has been involved in sperm capacitation). Although, the exact distribution of lipids raft during capacitation still unclear. We searched these changes during mouse sperm capacitation and its effects in fertilization. Sperm were incubated in HMB medium (capacitation) 60’ or PBS buffer (control) 10’, 37ºC and 5% CO2. Later were fixed and marked: cholesterol by filipin III (FIII) and sphingolipids (GM1) by fraction b cholera toxin (bCT). FIII is self-fluorescent and bCT is conjugated with Alexa FluorÒ. Samples were observed in a fluorescence microscope. Sperm (capacitated and control) showed different fluorescence standards with FIII and bCT, probably due to a lipidic redistribution on sperm surface. In fecundation in vitro assay, we blocked lipids raft preincubating sperm with bCT (GM1) 15’. Then, sperm were coincubated with Hamster oocyte, and the sperm bounded were counted. First observations showed a binding decrement in sperm blocked with bCT (GM1) comparing with the control (not blocked). These results suggest that GMI (Sphingolipid), a classic raft component, and its redistribution after capacitation are involved in sperm – oocyte binding.