EFFECTS OF CAPACITATION AND ACROSOME REACTION ON RAT SPERMATOZOA LIPIDS AND FATTY ACIDS

ZANETTI S; MONCLUS M A; AVELDAÑO M; FORNES M W

Rosario

Congreso; XLII Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2006

SAIB

EFFECTS OF CAPACITATION AND ACROSOME REACTION ON RAT SPERMATOZOA LIPIDS AND FATTY ACIDS Zanetti SR; Monclus MA; Aveldaño MI and Fornés MW IHEM, CONICET-UNC, 5500 Mendoza e INIBIBB, CONICET-UNS, 8000 Bahía Blanca, Argentina. Mammalian spermatozoa must mature (capacitate) before they can undergo the acrosome reaction (AR) that enable them to fertilize an egg. The mechanisms underlying these events have not yet been fully elucidated. In this work we focused on the effects of these sperm functions on the amounts and fatty acid composition of the main lipid classes of mature rat spermatozoa. Capacitation was assessed by a protein tyrosine phosphorylation assay, and AR was induced by stimulation of spermatozoa with A23187/Ca2+ in the presence of albumin. Capacitation resulted in a significant loss of cholesterol and phospholipids (PL) from sperm. In acrosome-reacted spermatozoa, part of the PL were hydrolyzed, as reflected in the generation of diacylglycerol, phosphatidic acid, and free arachidonic acid (20:4n-6). The amounts per cell of the male germ-cell specific sulfogalactolipid (seminolipid), as those of sphingomyelin and ceramide, remained similar to controls in capacitated and acrosome-reacted spermatozoa, thus increasing their proportions in relation to PL. The latter two sphingolipids contained high percentages of very long chain polyunsaturated fatty acids, both non-hydroxylated and 2-hydroxylated. The lipid changes may work synergistically with protein phosphorylation to convert an initially stable into a fusion-competent membrane, capable of engaging in fertilization-promoting events.