ARTICLE

STRUCTURE OF MEMBRANE HOLES IN OSMOTIC AND SAPONIN HEMOLYSIS

P. Seeman ¹, D. Cheng ¹, and G. H. Iles ¹

¹ From the Department of Pharmacology and the Institute of Biomedical Electronics, University of Toronto, Toronto 5, Ontario, Canada.

Dr. Cheng's present address is The Rockefeller University, New York 10021.

Serial section electron microscopy of hemolysing erythrocytes (fixed at 12 s after the onset of osmotic hemolysis) revealed long slits and holes in the membrane, extending to around 1 µm in length. Many but not all of the slits and holes (about 100–1000 Å wide) were confluent with one another. Ferritin and colloidal gold (added after fixation) only permeated those cells containing membrane defects. No such large holes or slits were seen in saponin-treated erythrocytes, and the membrane was highly invaginated, giving the ghost a scalloped outline. Freeze-etch electron microscopy of saponin-treated membranes revealed 40–50 Å-wide pits in the extracellular surface of the membrane. If these pits represent regions from which cholesterol was extracted, then cholesterol is uniformly distributed over the entire erythrocyte membrane.

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