Glutamic-pyruvic transaminase activity related to red blood cell age

Red blood cell glutamic-pyruvic transaminase (GPT) phenotypes and catalytic activities were studied in normal subjects and in patients with various hemolytic syndromes associated with reticulocytosis. To assess the effect of cell age of GPT activity, young cells were separated from older cells by centrifugation, and the catalytic activities were compared. In normal blood, there was a progressive fall in GPT activity from the top layer (younger cells) to the bottom layer (older cells), with a mean ratio of 1.90 plus or minus 0.42. Similarly, in the blood of patients with reticulocytosis, the enzyme activity of the reticulocyte-rich layer was higher than that of the layer containing older cells (mean ratio 1.94 plus or minus 0.95).