Changes in rat spermatozoa sphingolipids during epididymal maturation and acrosome reaction

ZANETTI, S. R.; MONCLUS M; RENSETTI D; AVELDAÑO M; FORNÉS M

Potrero de los Funes, San Luis

Congreso; XXIV Reunión Científica Anual de la Sociedad de Biología de Cuyo – 2006 - IV Reunión de la Sociedad de Microscopía; 2006

Sociedad de Biología de Cuyo

Changes in rat spermatozoa sphingolipids during epididymal maturation and acrosome reaction Zanetti S, Monclus M, Rensetti D, Aveldaño M and Fornés M IHEM, CONICET-UNC, 5500 Mendoza e INIBIBB, CONICET-UNS, 8000 Bahía Blanca, Argentina. e-mail: szanetti@criba.edu.ar During their epididymal transit spermatozoa undergo a series of changes -maturational and capacitated changes - 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 their effects on the amounts and fatty acid composition of the main sphingolipid class of mature rat spermatozoa. Sphingomyelin (SM) and ceramide (Cer), lipids that in previous work were shown to be typically rich in very long chain polyunsaturated fatty acids (VLCPUFA) in germinal cells from the rat testis, changed with epididymal maturation. The content of SM decreased but Cer increased, so the ratio Cer/SM increased from caput to cauda epididymidis, suggesting the activation of a sphingomyelinase. The proportion of SM-associated VLCPUFA such as 28:4n-6 tended to decrease in SM and to increase in Cer with sperm maturation. Capacitation was assessed by 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 increase of SM and Cer, and both increased additionally in acrosome-reacted spermatozoa as did the male germ-cell specific sulfogalactolipid (seminolipid), SM and Cer being richer than those of the starting cells in VLCPUFA, both non-hydroxylated and 2-hydroxylated. The sphingolipid changes may work synergistically with protein phosphorylation to convert an initially stable to a fusion-competent membrane, capable of engaging in the AR.