Selective stimulation of erythrocyte membrane phospholipid fatty acid turnover associated with decreased cell volume

Treatment of erythrocytes with the divalent cation ionophore A23187 results in net uptake of calcium and a calcium-dependent decrease in cellular potassium content and cell volume. These changes in membrane properties are associated with a selective stimulation of fatty acid incorporation into membrane phosphatidylethanolamine (PE). In this study the relationship between this selective stimulation of phospholipid fatty acid turnover and changes in calcium uptake, cellular potassium content, and cell volume has been examined by 1) preventing the calcium-dependent loss of potassium without abolishing calcium uptake and 2) altering cellular potassium content and cell volume without increasing net uptake of calcium by utilizing the monovalent cation inonophore nigericin or increasing the osmolarity of the buffer. It has been shown that treatment of erythrocytes with A23187, nigericin, or hypertonic buffer results in a selective stimulation of fatty acid incorporation into PE. These results suggest that a mechanical or conformational change in the membrane is associated with a selective stimulation of fatty acid turnover in phosphatidylethanolamine.