Composition and morphology of lipid droplets from oviduct epithelial cells

Abstract

This study was undertaken to determine the composition and morphology of lipid droplets in situ and isolated from oviductal epithelial cells and oviductal fluid. Oviductal epithelial cells were harvested enzymatically from oviducts of cows in either the luteal or the follicular stages of the ovarian cycle. Lipid droplets were isolated from cellular homogenates and characterized biochemically using thin layer chromatography. The morphology of lipid droplets in oviductal epithelial cells and in fractions isolated by ultracentrifugation from cellular homogenates was examined by electron microscopy. Lipid droplets isolated from oviduct epithelial cells varied in composition with the ovarian cycle and the oviductal region. There was more total lipid in droplets isolated from cows in the luteal than follicular phase of the ovarian cycle. Most of this difference was due to large amounts of esterified cholesterol present in the samples from luteal-stage animals. The most esterified cholesterol was found in droplets isolated from the oviductal isthmus of luteal cows. Droplets similar in lipid composition to those isolated from epithelial cells were found in oviductal fluid. Four distinct types of lipid inclusions were evident in electron micrographs of oviductal epithelia and characterized as osmiophilic droplets, lipofuscin-like clusters, lamellar structures, and composite bodies. All of the lipid inclusions were found in droplet isolates except for the extracted lipid portion of the composite body. The presence and diversity of oviduct epithelial lipid inclusions suggest that the oviductal epithelium may be very active in lipid metabolism, particularly cholesterol dynamics.