VERY LONG CHAIN POLYUNSATURATED FATTY ACIDS ARE THE MAJOR ACYL GROUPS OF SPHINGOMYELINS AND CERAMIDES IN THE HEAD OF MAMMALIAN SPERMATOZOA

FURLAND, NATALIA EDITH; ORESTI, GERARDO MARTÍN; ANTOLLINI, SILVIA SUSANA; VENTURINO, ANDRÉS; MALDONADO, EDUARDO NÉSTOR; AVELDAÑO, MARTA ISABEL

JOURNAL OF BIOLOGICAL CHEMISTRY

AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC

Año: 2007 vol. 282 p. 18151 - 18161

0021-9258

Very long chain (C24 to C34) polyunsaturated fatty acids (VLCPUFA) are important constituents of sphingomyelin (SM) and ceramide (Cer) in testicular germ cells. In the present paper we focused on the SM and Cer and their fatty acids in spermatozoa and their main regions, heads and tails. In bull and ram spermatozoa, SM was the third most abundant phospholipid (PL) and VLCPUFA were the major acyl groups (~70%) of SM and Cer. In rat epididymal spermatozoa the SM/ Cer ratio was low in the absence, and could be maintained high in the presence, of the cation chelator EDTA, added to the media used for sperm isolation. This fact points to the occurrence of an active divalent cation-dependent sphingomyelinase. Bull and rat sperm had an uneven head-tail distribution of PL, with virtually all the VLCPUFA-rich SM located at the head, the lower SM content in the rat being determined by the lower sperm head/ tail size ratio. Most of the SM from bull sperm heads was readily solubilized with 1% Triton X-100 at 4ºC. The detergent-soluble SM fraction was richer in VLCPUFA than the non-soluble fraction, richer in saturated fatty acids. Cer was produced at the expense of SM, thus decreasing several-fold the SM/ Cer ratio, in rat spermatozoa incubated for 2 h in presence of the sperm capacitating agents, calcium, bicarbonate and albumin. The generation of Cer from SM in the sperm head surface may be an early step among the biochemical and biophysical changes known to take place in the spermatozoon in the physiological events preceding fertilization.