Cholesterol is enriched in the sphingolipid patches on the substrate near nonpolarized MDCK cells, but not in the sphingolipid domains in their plasma membranes.

Information about the distributions of cholesterol and sphingolipids within the plasma membranes of mammalian cells provides insight into the roles of these molecules in membrane function. In this report, high-resolution secondary ion mass spectrometry was used to image the distributions of metabolically incorporated rare isotope-labeled sphingolipids and cholesterol on the surfaces of nonpolarized epithelial cells. Sphingolipid domains that were not enriched with cholesterol were detected in the plasma membranes of subconfluent Madin-Darby canine kidney cells.

Three-dimensional imaging of cholesterol and sphingolipids within a Madin-Darby canine kidney cell.

Metabolic stable isotope incorporation and secondary ion mass spectrometry (SIMS) depth profiling performed on a Cameca NanoSIMS 50 were used to image the (18)O-cholesterol and (15)N-sphingolipid distributions within a portion of a Madin-Darby canine kidney (MDCK) cell. Three-dimensional representations of the component-specific isotope distributions show clearly defined regions of (18)O-cholesterol and (15)N-sphingolipid enrichment that seem to be separate subcellular compartments. The low levels of nitrogen-containing secondary ions detected at the (18)O-enriched regions suggest that these (18)O-cholesterol-rich structures may be lipid droplets, which have a core consisting of cholesterol esters and triacylglycerides.