Colloidal Iron Stain for Distinguishing Open from Sealed Endocytic Vesicles of Erythrocytes 1

Abstract

Abstract

Ferritin-labeled antibodies and lectins have been used to visualize endocytic vesicles in erythrocytes. Distinguishing preformed endocytic vesicles from invaginated plasma membrane has proved difficult especially since antibodies and lectins by themselves induce these changes in membrane configuration. We have used a transmission electron microscope technique (TEM) utilizing positive colloidal iron staining, employing as our model erythrocytes treated with cationic amphipathic drugs. Our technique allows fixation of cells at any point during drug treatment before staining. The membrane lining of unsealed but not of sealed vesicles was coated with electron dense ferric oxide grains. The formation of sealed vesicles is evidence for the fluidity of membranes of the erythrocytes of adults. The data also suggest that the mechanism may not be identical with every cationic amphiphile.