Abstract
The specific activities of some glucose and glycogen degradative enzymes were studied in serially subcultured fibroblasts harvested at the same state of growth and replication. A continuous increase in the activities of phosphofmctokinase, lactate dehydrogenase, and glycogen phosphorylase was noted beyond passage 10 equalling 677 ± 74.8,170 ± 34.1, and 317 ± 57.6% of control activity at passage 25, respectively. There was a concurrent increase in the glycogen content of cells reaching a maximum of 1,498 ± 223% of control at passage 15 and maintained nearby at passages 20 and 25. Citrate synthase activity was profoundly increased at passage 15 but drastically dropped at passages 20 and 25. There were no significant variations in the above parameters between passages 1 and 10 of subculture. This enhancement of glycolytic activity which accompanies the aging (subculture) process could not be depressed as a result of improved oxygenation of the cultures.