PHOSPHOINOSITIDE METABOLISM AND SHAPE CONTROL IN SHEEP RED-BLOOD-CELLS

Metabolic depletion of sheep red blood cells leads to decreased intrac ellular concentrations of ATP and reduced glutathione as well as degra dation of phosphoinositides. In sheep red blood cells, depletion of AT P induced two types of shape transformation: one early phase involving formation of protrusions on the cell surface similar to those observe d upon depletion of human red blood cells; and one late phase, in whic h the sheep red blood cells develop long, rod-shaped projections. Duri ng the initial stages of shape changes, degradation of the phosphoinos itides parallels the discocyte-echinocyte transformation, thus giving further support to a shape-controlling mechanism based on the bilayer- couple hypothesis. However, formation of the long projections does not coincide with turnover of the phosphoinositides but rather with the l evel of reduced glutathione. This indicates that development of these rod-like extensions on the cell surface is induced by oxidative proces ses that may well involve cross-linking of membrane skeleton proteins.