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Increased Polyamine Concentration and Tumor-derived Lactate Dehydrogenase Activity in Physiological Fluids during Regression of a Heterologous Tumor Transplant¹

AB Ferrosan, Fack, S-201 10 Malmö [G. A.] and Department of Zoophysiology, University of Lund, Helgonavägen 3, S-223 62 Lund, Sweden [G. B., A. A., S. R., O. H.]

Tumor cell death was induced by heterologous transplantation of an Ehrlich ascites tumor of the mouse into the peritoneal cavity of mongolian gerbils. The rate of tumor cell death was determined by measuring the loss of ¹²⁵I from tumor-bearing gerbils at various times after transplantation of 5-[¹²⁵I]iodo-2'-deoxyuridine-labeled mouse tumor cells.

Analyses of lactate dehydrogenase (LDH) isozyme patterns revealed that Ehrlich ascites tumor cells and gerbil serum only contained one of the isozymes, namely, LDH 5. Since LDH 5 of the mouse tumor cells was electrophoretically different from LDH 5 of the gerbil serum, it was possible to identify and quantitate tumor-derived isozyme in serum of the gerbil during the entire course of tumor regression.

The activity of LDH and the concentration of polyamines in cell-free ascites fluid were at their peak levels at the time of maximal rate of tumor cell death and decreased rapidly during the period of final elimination of the tumor by the host. In serum the LDH activity and the polyamine concentration reached their peak levels somewhat later, probably reflecting the time required for clearance of these compounds from ascites fluid into serum.

The polyamine concentration in cell-free ascites fluid and serum was correlated with the activity of tumor-derived LDH in these fluids. High positive correlations were observed, suggesting that the increase in polyamine level which occurs during tumor regression is due to release of polyamines from dead or dying tumor cells.

¹ Supported by Swedish Cancer Society Grant 959-B76-01X and by gifts from the Royal Physiographical Society.

Received 3/27/78. Accepted 8/17/78.