68. Linoleic acid increases neutral lipid storage during bovine oocyte maturation

Efficient utilization of bovine oocytes for in vitro embryo production requires successful cryopreservation. However, oocyte development to the blastocyst stage is low after oocyte cryopreservation (Martino et al., 1996). Linoleic acid (LA) is an essential long-chain unsaturated fatty acid (FA), with positive effects reported on cryopreservation. The use of this FA in the culture medium increased the survival rate of frozen-thawed enucleated oocytes and embryos (Hochi et al., 1999, 2000; Tominaga et al., 1999). This effect could be due to an increase in membrane fluidity as a result of the incorporation of an unsaturated FA, preventing their rupture during freezing. According to Pereira and Marques (2008), cold cell damage is mainly due to physical changes experienced by lipids at low temperatures, in particular, intracellular lipids play a major role in the cryosensitivity of oocytes (Nagashima et al., 1995). The aim of this study was to evaluate the effect of LA on intracellular lipid droplets content and its impact on viability of vitrified oocytes. Cumulus oocyte complexes (COC) aspirated from ovaries recovered after slaughter were in vitro matured in a chemically defined maturation medium supplemented with LA at 9, 43 and 100 μM and were denuded and fixed. Oocytes were stained with 1 μg/ml Nile Red in PBS for 10 min. Digital photographs were taken using an epifluorescence microscope and fluorescence intensity was measured with the software Nis Elements Br 3.1. As validated by other authors (Barcelo Fimbres and Seidel 2011), the intensity of fluorescence correlates mainly with the content of triacylglycerols in lipid droplets. Results showed an increase in the mean fluorescence at all concentrations of LA (9, 43 and 100 μM) corresponding to an increase of 17.3, 47.4 and 57.3%, over the control ( p