Double labeling of lipoprotein receptors in fibroblast cell surface replicas

Using gold particles of distinctly different sizes as markers, the simultaneous visualization of two types of lipoprotein binding sites in surface replicas of the human fibroblast plasma membrane was achieved. Double-labeling experiments based on this principle have been carried out using sequential or simultaneous exposures of fibroblast cultures to a variety of lipoprotein species. Examples of the results obtained are illustrated, and the application of this approach to the analysis of the distribution, the relationship between, and the specificity of different classes of receptor is discussed.