Neutral lipid droplets in bovine oviductal epithelium and lipid composition of epithelial cell homogenates.

This study was undertaken to locate and to quantify lipids within the oviduct epithelial cells that might serve as a source of luminal lipids. Oviduct epithelial cells were analyzed from 12 cows in either the follicular or luteal stage of the ovarian cycle. Histochemical differences in neutral lipid droplets and phospholipids containing choline were detected among the oviductal regions. Neutral lipid staining was greatest in the preampulla and the ampulla and least in the isthmus. Staining of phospholipids containing choline was similar in preampullary and ampullary epithelia but was concentrated in isthmic crypts. Neutral lipid droplets, detected fluorescently with Nile Red, were present in a greater percentage of preampullary epithelial cells (76.8 +/- 1.8) than ampullary (42.1 +/- 2.1) or isthmic cells (12.2 +/- 1.3). Neither ovarian cycle stage nor side of ovulation affected the concentration of epithelial lipid droplets. Colorimetric lipid assays determined that concentrations of free cholesterol and glycerides in the preampulla were higher than in other regions. Most esterified cholesterol was detected in the isthmus. These findings indicate that the bovine oviduct epithelium exhibits regional differences in phospholipid and neutral lipid distribution. Because many of the lipids studied affect gamete and early embryo membranes, localization differences may affect the functional variability of the oviductal regions.