title: Fatty acid composition of lipids in immature cattle, pig and sheep oocytes with intact zona pellucida.
abstract: Cattle, pig and sheep oocytes isolated from healthy cumulus-oocyte complexes were pooled, within species, to provide samples of immature denuded oocytes with intact zona pellucida (n = 1000 per sample) for determination of fatty acid mass and composition in total lipid, constituent phospholipid and triglyceride. Acyl-containing lipid extracts, transmethylated in the presence of a reference penta-decaenoic acid (15:0), yielded fatty acid methyl esters which were analysed by gas chromatograph. Mean (+/- SEM) fatty acid content in samples of pig oocytes (161 +/- 18 micrograms per 1000 oocytes) was greater than that in cattle (63 +/- 6 micrograms; P < 0.01) and sheep oocytes (89 +/- 7 micrograms; P < 0.05). Of 24 fatty acids detected, palmitic (16:0; 25-35%, w/w), stearic (18:0; 14-16%) and oleic (18:1n-9; 22-26%) acids were most prominent in all three species. Saturated fatty acids (mean = 45-55%, w/w) were more abundant than mono- (27-34%) or polyunsaturates (11-21%). Fatty acids of the n-6 series, notably linoleic (18:2n-6; 5-8%, w/w) and arachidonic acid (20:4n-6; 1-3%), were the most abundant polyunsaturates. Phospholipid consistently accounted for a quarter of all fatty acids in the three species, but ruminant oocytes had a lower complement of polyunsaturates (14-19%, w/w) in this fraction than pig oocytes (34%, w/w) which, for example, had a three- to fourfold greater linoleic acid content. An estimated 74 ng of fatty acid was sequestered in the triglyceride fraction of individual pig oocytes compared with 23-25 ng in ruminant oocytes (P < 0.01). It is concluded that the greater fatty acid content of pig oocytes is primarily due to more abundant triglyceride reserves. Furthermore, this species-specific difference, and that in respect of polyunsaturated fatty acid reserves, may underlie the contrasting chilling, culture and cryopreservation sensitivities of embryos derived from pig and ruminant (cattle, sheep) oocytes.
authors.affiliation: Scottish Agricultural College, Animal Biology Division, Bucksburn, Aberdeen, UK.
authors.forename: T G
authors.initials: TG
authors.lastname: McEvoy
authors.forename: G D
authors.initials: GD
authors.lastname: Coull
authors.forename: P J
authors.initials: PJ
authors.lastname: Broadbent
authors.forename: J S
authors.initials: JS
authors.lastname: Hutchinson
authors.forename: B K
authors.initials: BK
authors.lastname: Speake
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D016718:Arachidonic Acid / Q000032:analysis; D002417:Cattle; D002849:Chromatography, Gas; D005227:Fatty Acids / Q000032:analysis*; D005260:Female; D019787:Linoleic Acid / Q000032:analysis; D008055:Lipids / Q000737:chemistry*; D019301:Oleic Acid / Q000032:analysis; D009865:Oocytes / Q000737:chemistry*; D019308:Palmitic Acid / Q000032:analysis; D010743:Phospholipids / Q000737:chemistry; D012418:Ruminants / Q000378:metabolism*; D012756:Sheep; D013045:Species Specificity; D013229:Stearic Acids / Q000032:analysis; D013552:Swine / Q000378:metabolism*; D014280:Triglycerides / Q000737:chemistry
chemical_list: D005227:Fatty Acids; D008055:Lipids; D010743:Phospholipids; D013229:Stearic Acids; D014280:Triglycerides; D016718:Arachidonic Acid; D019301:Oleic Acid; D019308:Palmitic Acid; D019787:Linoleic Acid