Lipids play an important role in the maturation, viability and function of sperm cells. In this study, we examined the neutral and polar lipid composition of boar spermatozoa by thin-layer chromatography/mass spectrometry. Main representatives of the neutral lipid classes were diacylglycerols containing saturated (myristoyl, palmitoyl and stearoyl) fatty acyl residues. Glycerophosphatidylcholine and glycerophosphatidylethanolamine with alk(en)yl ether residues in the sn-1 position and unsaturated long chained fatty acyl residues in sn-2 position were identified as the most prominent polar lipids. The only glycoglycerolipid was sulfogalactosylglycerolipid carrying 16:0-alkyl- and 16:0-acyl chains. Using stable isotope-labelling, the metabolic incorporation of exogenously supplied fatty acids was analysed. Boar spermatozoa incorporated hexadecenoic (16:1), octadecenoic (18:1), octadecadienoic (18:2) and octadecatrienoic (18:3) acids primarily in the diacylglycerols and glycerophosphatidylcholines. In contrast, incorporation of eicosapentaenoic acid (20:5) was not detected. The analysis of molecular species composition subsequent to the incorporation of exogenous [(14)C]-octadecadienoic acid suggests two pathways for incorporation of exogenous fatty acids into glycerophosphatidylcholine: (1) de novo synthesis of glycerophosphatidylcholine via the CDP-choline pathway and (2) reacylation of lysophosphatidylcholine via an acyltransferase.
Keywords: AA; BTS; Beltsville Thawing Solution; Boar spermatozoa; DAG; DHB; Diacylglycerol; FFA; Fatty acid; GC; GPA; GPC; GPE; GPI; GPL; GPS; Glycerophospholipid; LPC; MAG; MS; PLA(2); PLC; SGG; TLC; aminoacridine; diacylglycerol; dihydroxybenzoic acid; free fatty acids; gas chromatography; glycerophosphatidic acid; glycerophosphatidylcholine; glycerophosphatidylethanolamine; glycerophosphatidylinositol; glycerophosphatidylserine; glycerophospholipid; lyso-glycerophosphatidylcholine (monoacylglycerophosphatidylcholine); mass spectrometry; monoacylglycerol; phospholipase A(2); phospholipase C; sulfogalactosylglycerolipid; thin-layer chromatography.
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