Figure 3.

Using Ruthenium red (Ru red) to label the cell surface, single vesicles (arrows) as well as caveolar clusters (arrowheads) are found to be Ru red-positive. This finding indicates that they are still in connection with the cell surface. Note that many of the vesicles deeper in the cytoplasm are also labelled with Ru red showing that they are still connected with the cell surface. The caveolar clusters (arrowheads) are often described as caveosomes. The Ru red staining clearly shows that many of them are not independent structures. pm: plasma membrane. Bars: 400 nm.