Intramembranous particle distribution in human erythrocytes: Effects of lysis, glutaraldehyde, and poly‐L‐lysine

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Abstract
Freeze‐fracture combined with quantitative electron microscopy of the intact human erythrocyte (RBC) and ghost revealed significant differences in their intramembranous particle coefficients. External (E) fracture‐faces of unfixed ghost membranes were found to contain 40% fewer particles than those of intact unfixed RBC. The particle distribution of the intact RBC membrane depended on the use of glutaraldehyde fixation and glycerol cryoprotection. Whereas glutaraldehyde‐ and glycerol‐treated cells disclosed 70% fewer E‐face particles than did intact unfixed cells, poly‐L‐lysine‐treated, intact, unfixed RBC showed no such differences. Treatment with a combination of poly‐L‐lysine and glutaraldehyde, however, increased the amount of E‐face particles while reducing those of the protoplasmic (P) face. The poly‐L‐lysine effect varied with its concentration and was unaffected by previous application of neuraminidase. Nor did the lectin phytohemagglutinin induce particle rearrangement in intact cells. Our data demonstrate that the processes of glutaraldehyde fixation and glycerol cryoprotection modify the RBC membrane by decreasing the number of E‐face particles present. In addition, the combination of poly‐L‐lysine and glutaral‐dehyde alters the affinity of some particles for one half of the membrane, suggesting that in freeze‐fractured RBC, chemical bonds formed at the extracellular surface of the membrane can influence particle partitioning.