The Effect of Potassium on the Growth of Normal and Malignant Cells in Tissue Culture *

Potassium is the dominant cation of the cell, but in the body fluids sodium dominates. This remarkable fact has been the stimulus to many investigations of normal and malignant tissues.'4 Analysis of tumor tissue has shown, in general, an increase in potassium which is roughly proportional to the rate of growth." 2,18 Roffo"2 states that the potassium content of rat tumor was about the same as that of rat embryos. According to Negre," and also to H'andel,9 transplantable tumors of mice took successfully in a higher proportion of instances and grew more rapidly in mice previously fed diets high in potassium. Goldzieher7 and Goldzieher and Rosenthal8 obtained similar effects following intraperitoneal injections of potassium salts in mice. Analogous experiments with the rabbit by Tokunaga and Nagaoka"7 had the same result, but Sugiura and Benedict"5 could not confirm these findings in rats. In ABC albino mice rendered deficient in potassium the growth of tumor 15091a was found in our laboratory'0 to be significantly retarded, but large, well-established, rapidly growing tumors were not significantly influenced in their growth by removing potassium from the diet. Experiments with tumor and normal tissues in culture were made by Roffo,"3 but the interpretation of these experiments was made difficult since more than one factor was varied and exact quantitative methods were not employed. This writer concluded that increase of potassium in the media enhanced the growth of both normal and malignant tissues. Tissue culture affords a quantitative method of determining the results of known changes in the environment of the cell. In the present experiments the effect of equimolecular substitution of K+ for Na+ on the growth of normal and malignant cells was investigated.