Lipid biochemical and biophysical changes after rat sperm capacitation and acrosomal reaction.

ORESTI, G.M.; PEÑALVA, D.A.; LUQUEZ, J.M.; ANTOLLINI, S.S.; AVELDAÑO, M.I.

San Luis

Congreso; XLVII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2011

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Recent work showed that sperm capacitation and acrosomal exocytosis, when induced in vitro in rat spermatozoa, are accompanied by hydrolysis of specific lipid classes. Here, we aimed at studying how these reactions affect the biophysical properties of the sperm total lipid. In contrast to ejaculated sperm, in spermatozoa that are isolated from cauda epididymes a rapid uptake of extracellular calcium occurs that leads to many of them undergoing a premature acrosomal exocytosis. To avoid this ?spontaneous? process, we included EDTA in all media used for sperm isolation from rat epididymis. This prevented the partial hydrolysis of sperm head-located sphingomyelin to ceramide and of main glycerophospholipids to lysophospholipids and free fatty acids or diglycerides. Significant increases in the generalized polarization of the fluorescent probe Laurdan were observed between liposomes prepared from the lipid of these controls, of gametes isolated with no EDTA, and of those incubated in conditions that promote their capacitation and acrosomal reaction. Interestingly, the hydrolysis of main glycerophospholipids evoked by the latter reactions affected mostly the 1,2-diacyl subclasses, the gametes thus becoming relatively enriched in plasmalogens. Our data suggest that the lipid changes that occur during these physiologically relevant processes encourage an increase in sperm membrane order.