Growth of the U.C.L.A. fibrosarcoma and the Jensen sarcoma in male and female rats of the Long-Evans strain has been investigated with and without the influence of dl-ethionine. Total and “free” amino acids (serine, threonine, methionine, arginine, glycine) have been determined in the livers of the rats by microbiological assay methods.

The administration of dl-ethionine retarded the growth of tumors, increased the tendency of tumors to regress, produced necrosis in all tumors examined, and, in nontumor-bearing animals, caused a marked increase in the “free” amino acids of the liver. There was also noted an increase in “free” amino acid content of livers of rats bearing large tumors. The weight of the liver was maintained proportional to the body weight (carcass plus tumor).

It was concluded that, when acting in conjunction with strong natural inhibitors, dl-ethionine is an effective regressing agent under the described experimental conditions.


Paper No. 95. For the preceding related paper (No. 80) see Montañez et al. (6). This work was aided by grants from the University of California. The authors are indebted to Dr. M. N. Camien, for assistance in the microbiological assays, and to Dr. Puliyur K. Vijayarhavan for preliminary tumor studies with ethionine.

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