Fatty acid profile of blood plasma and oviduct and uterine fluid during early and late luteal phase in the horse

During early pregnancy, the secretome of both oviduct and uterus serves as exchange medium for signaling factors between embryo and mother and provides the embryo with nutrients. The preimplantation embryo can utilize the fatty acids (FA) therein via direct incorporation into cell membrane lipid bilayers and for energy production via β-oxidation. The FA concentration and composition of the oviduct (OF) and uterine fluid (UF) might be regulated by ovarian hormones to meet the changing needs of the growing embryo. In our study, we analyzed the FA profile of blood plasma (BP) and reproductive fluid samples obtained post mortem from slaughtered mares by gas chromatography mass spectrometry. Cycle stage was determined by visual evaluation of the ovary and measurement of plasma progesterone. No major effect of cycle stage on the FA profile was observed. However, the composition of FA was different between BP and both OF and UF. While linoleic, stearic, oleic and palmitic acid were the four most prevalent FA in both BP and reproductive fluids, the latter contained higher concentrations of arachidonic, eicosapentaenoic and dihomo-γ-linolenic acid. The finding suggests selective endometrial transport mechanisms from plasma into the reproductive fluids or increased endometrial synthesis of selected FA.