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Kinetics of Cell Proliferation and Polyamine Synthesis during Ehrlich Ascites Tumor Growth¹

Department of Zoophysiology, University of Lund, Helgonavägen 3, S-223 62 Lund, Sweden

The kinetics of cell proliferation and polyamine synthesis during Ehrlich ascites tumor growth were studied. The steady deceleration of the specific growth rate with increasing tumor mass that was observed was attributable to a prolongation of the cell cycle, particularly of the S and G₂ phases. The cell cycle time (T_C) was 43.3 hr (T_G1 = 10.8, T_S = 26.8, and T_G2 = 5.7 hr) on the seventh day of growth and 76.0 hr (T_G1 = 14.0, T_S = 52.0, and T_G2 = 10.0 hr) on the tenth day of growth. The growth fraction showed a decrease from 0.77 to 0.60 during the 7- to 10-day tumor growth interval. The cell death rate remained low and essentially unchanged during this period. A high correlation was found between polyamine synthesis (ornithine decarboxylase activity) and the specific growth rate; the correlation coefficient was 0.985. There was also a high positive correlation between the cellular polyamine (spermidine and spermine) and nucleic acid content (spermidine:DNA = 0.916, spermine:DNA = 0.947, spermidine:RNA = 0.907, and spermine:RNA = 0.881). These observations suggest that there may be a functional coupling between polyamines and nucleic acids, and they support the hypothesis that polyamines play an important role in DNA replication and cell division.

¹ This investigation was supported by Swedish Cancer Society Grant 959-B76-01X and by gifts from the Royal Physiographical Society.

Received 5/23/77. Accepted 8/11/77.