Red blood cell lipids and the plasma membrane

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Abstract
The red‐blood cell occupies a unique position both in the historical development of membrane theory and current experimentation on membrane properties. The cell is readily accessible and has been studied in many animal species and disease conditions. Differences in composition, structure, and properties have been described, and a num‐ber of highly specific cell types are now available for investigation.Several techniques are used to study the mem‐brane of the intact cell. The membrane surface may be labeled in specific areas by the selective exchange of lipids such as cholesterol. Exchange studies provide information about lipid‐lipid and lipid‐protein interactions in the intact structure‐Membrane lipids are hydrolyzed by phospho‐lipases, and enzymatic activity is modified by the action of penetrating hemolytic agents. Perme‐ability is readily measured by hemolysis and correlated with chemical structure, partition coefficient, and biological activity of different metabolites and drugs. The red cells of Vitamin B‐deficient animals are particularly susceptible to hyperoxia. Hemolysis in these cells is correlated with alterations in membrane structure through the formation of lipid peroxides.Gorter and Grendel first used monolayers pre‐pared from red‐cell lipids to show that sufficient lipid was present in the membrane to form a bimolecular layer. Lipids extracts from the red cells of different animal species and disease states have been used in recent monolayer studies. The surface properties of these lipids and their purified neutral lipid and phospholipid fractions yield ad‐ditional information about lipid‐lipid interactions which may exist in the membrane. Enzyme hy‐drolysis and penetration studies indicate that lipids in monolayers and membranes have similar properties.