A primary effect of palmitic acid on mouse oocytes is the disruption of the structure of the endoplasmic reticulum.
Exposure of mouse oocytes to saturated fatty acids such as palmitic acid has been shown to increases lipid content and cause an endoplasmic reticulum stress response and changes in the mitochondrial redox state. The links between these changes, or whether they are prevented by mono-unsaturated fatty acids such as oleic acid is unclear. Here, we have investigated the effects of fatty acids on mouse oocytes, that are maturated in vitro, using coherent anti-Stokes Raman scattering and two-photon fluorescence microscopy. When oocytes were matured in the presence of palmitic acid there were changes in the aggregation pattern and size of lipid droplets. Maturation in palmitic acid alone also caused a distinctive disruption of the endoplasmic reticulum structure. This effect was prevented by incubation of oleic with palmitic acid. In contrast, maturation of mouse oocytes in medium containing palmitic acid was not associated with any significant change in the redox state of mitochondria or the Ca2+ content of intracellular stores. These data suggest that a primary effect of saturated fatty acids such as PA on oocytes, is to disrupt the structure of the endoplasmic reticulum and this is not due to any other effect on mitochondria or Ca2+ stores.