Ionic calcium content of light dense human red cells separated by Percoll density gradients

In this paper we have compared the adequacy of two methods using Percoll density gradients to separate light and dense erythrocytes from fresh human blood. After measuring the distribution of some classical age-markers such as haemoglobin, potassium and creatine contents, it was found that preformed gradients generated more stringent conditions for age-related density separations. Employing such gradients the free Ca2+ content of above sub-populations was assessed with Fura-2, under conditions where the viscosity effect was abolished. In five experiments, the free Ca2+ content (mean value +/- 1 S.D.) was 8.4 +/- 2.82 nM and 31.2 +/- 13.0 nM for the 7-10% lightest and densest cells, respectively. These results are discussed in connection to red cell senescence.