Abstract
Guinea pig, rat and sheep erythrocytes were sized electrically using the hydrodynamic focusing technique. The experimental curves were approximated with a computer by linear and logarithmic normal distributions. Rat and guinea pig erythrocytes from adult animals were best approximated by one linear normal distribution. Two populations (I, II) of erythrocytes with different mean volume could be demonstrated in young guinea pigs by this analysis. Population I erythrocytes are small, have a lower electrophoretic mobility and are mainly present at birth. They are gradually replaced by the larger population II erythrocytes. Both types of erythrocytes are probably the result of separate differentiation pathways. The analysis of erythrocyte volume distribution curves during immune lysis by antibody and complement shows that intact and ghost erythrocytes are measured by electrical sizing. No volume changes were observed up to the EAC1-8 intermediate. After the addition of C9, a C9 dose-dependent part of the erythrocytes swell permanently to spheroids. The spheroid transformation is a temperature-dependent, all or nothing reaction which is independent of protein osmotic forces from the interior of the cell.