3-DIMENSIONAL ULTRASTRUCTURE OF IN-SITU MEMBRANE SKELETONS IN HUMAN ERYTHROCYTES BY QUICK-FREEZING AND DEEP-ETCHING METHOD

The erythrocyte membrane skeleton is a network of some structural prot eins, principally composed of spectrin, actin and protein 4.1, which i s also attached to the cytoplasmic surface of the lipid membrane. The purpose of the present review is to describe the three-dimensional ult rastructure of in situ membrane skeletons in human erythrocytes. The i n situ membrane skeletons are densely organized, and the spectrin itse lf has a property of extension or contraction with reacting the extern al mechanical forces. The lengths between the intersections are change d according to the mechanical strength, and also vary even in one eryt hrocyte. To clarify the in situ organization of membrane skeletons, th e quick-freezing and deep-etching method should be used for fresh unfi xed erythrocytes because of their fragility during preparation steps.