Shape and volume changes in rat erythrocytes induced by surface-active alkyltrimethylammonium salts and sodium dodecyl sulphate.

Surface-active alkyltrimethylammonium salts (C12, C14 and C16) and sodium dodecyl sulphate (SDS) caused shape alterations and a volume increase in rat erythrocytes. The alkyltrimethylammonium salts caused echinocytic shapes at both prelytic and lytic concentrations during the first minutes of incubation at 37 degrees C but as the incubation proceeded some of the echinocytes were transformed into stomatocytes. This transformation developed through the normal discocyte shape and it occurred only above certain concentrations. With C14 and C16 the concentration at which stomatocytic shapes appeared coincided with those at which the volume increase began. With the C12 homologue stomatocytic shapes did not appear until lytic concentrations were reached, whereas the volume increase began at prelytic concentrations. SDS caused only echinocytic shapes at 37 degrees C and these appeared at prelytic concentrations, whereas the volume increase was associated with lytic concentrations. When erythrocytes crenated by SDS were cooled to room temperature they were transformed into stomatocytes and discocytes. Our results indicate that (a) even though ionic surfactants induce both swelling and shape alterations in erythrocytes these two changes are not necessarily connected, and that (b) the different shapes induced by cationic and anionic surfactants cannot be due to differences in the distribution of the surfactant molecules within the lipid bilayer of the erythrocyte membrane alone.