Calcium does not mediate the shape change that follows ATP depletion in human erythrocytes

Crenation, the shape change that follows ATP depletion in human erythrocytes, also follows ionphore-mediated Ca2+-loading. Experiments designed to test whether Ca2+ mediates metabolic crenation showed that: (1) an influx of extracellular Ca2+ is not required for metabolic crenation; (2) metabolic crenation is accompanied by a 70% increase in 86Rb+ permeability, a change much smaller than the increase expected if crenating concentrations of Ca2+ were released from bound intracellular pools; (3) A23187 plus EGTA, a treatment that depletes intracellular Ca2+ and stops Ca2+ crenation, does not affect metabolic crenation; (4) calmodulin inhibitors do not slow metabolic crenation. We conclude that Ca2+ does not mediate metabolic crenation. Albumin washes reverse Ca2+ crenation and metabolic crenation involve the accumulation of some amphiphilic species (e.g., lysolipid or diacylglycerol) in the cell membrane outer monolayer, and that ATP depletion induces a second crenating process which might be a reorganization of the cytoskeleton.