Constancy of cell volume during shape change of erythrocytes induced by increasing ATP content

Erythrocytes in long-preserved blood are spherical, but when the cells are incubated with inosine and adenine, the resulting increase in ATP content is accompanied by a shape change of the cells to discoidal form via a crenated form. The cells incubated with adenine alone or with no addition remain almost unchanged in shape. When incubated with inosine alone, the elevation in ATP level is less than that with both inosine and adenine, and the cell shape remains unchanged or changes partially into a crenated form. These phenomena occur in the presence of EDTA as well as in the absence of serum protein in the media. The cell volumes are measured as packed cell volume after centrifugation, by means of a Coulter counter (model S), and by determination of the intercellular space by the use of 131I-labeled bovine serum albumin. The results show that no alteration in cell volume occurs during the shape changes. Accordingly, the surface area of the cell must increase with increase in the ATP content. This suggests that both the lipid bimolecular layer and the undermembrane structure are altered during the shape change.