Erythrocytic calmodulin correlates with red cell age.

Red blood cells from normal persons and from patients with reticulocytosis were tested for their calmodulin content. Elevated calmodulin correlated with high reticulocyte counts, rather than with any specific disorder. The correlation between reticulocyte content and elevated calmodulin was further tested by fractionating the erythrocytes from 12 patients into reticulocyte-rich and reticulocyte-poor fractions. In the samples from each patient, erythrocytic calmodulin increased with increasing reticulocyte count.