[ALAD activity of red cells of different ages. (1st report) (author's transl)]

Rabbit erythrocytes were fractionated into populations of young cells (top layer) and old ones (bottom layer) by centrifugation, based on the fact that the specific gravity of young erythrocytes was lower than that of old ones. Then, reticurocyte count and osmotic resistance of red cells were compared between both populations. As a result, it has been obtained that many reticurocytes were found in the top layer, while none of those was found in the bottom layer. Furthermore, cells of the top layer were more resistant to hemolysis in the hypotonic media than those of the bottom layer. These findings suggested that the cell population of the top layer was young and that of the bottom layer was old. In comparison between both populations, the mean value of ALAD activity of young cells was 2.6 times higher than that of old ones. The rate of decrease of ALAD activity after intravenous administration of lead was similar in both populations while the amount of decrease of ALAD activity in the young cells was 2 to 3 times higher than that of the old ones.