Studies on the biological action of malononitriles. II. Distribution of rhodanese (transulfurase) in the tissues of normal and tumor-bearing animals and the effect of malononitriles thereon.

INTRODUCTION The enzyme rhodanese, which catalyzes the for mation of thiocyanate from cyanide and thiosulfate, is of interest to the cancer problem for reasons to be mentioned below. The administration of nitriles causes an increase in the thiocyanate level of the blood and in its urinary excretion. In seeking an explanation for the growth-retarding effect of certain substituted malononitriles and the lack of effect of others (4), it appeared logical to us to study the relations of this enzyme to tumors and the effect of the malononitriles thereon. Mendel, Rudney, and Bowman (7) reported that rat tissues (including malignant tumors) which exhibit a high aerobic glycolysis contain negligible rhodanese activity, while tissues in which glycolysis is suppressed by oxygen have high rhodanese activity. The low rhodanese ac tivity of tumor tissues has been reaffirmed by Rosen thai (8, 10), and low values were also found in many tissues with a normal aerobic metabo lism. The above reports appeared only as ab stracts without details or numerical values. Himwich and Saunders (5), in an investigation of the tissues of normal dogs, found disagreement be tween their results and those of the above-men tioned authors. On this point it should be men tioned that Rosenthal has noted that there are quite pronounced species differences in the activity of rhodanese of homologous tissues (8). Mendel et al. (7), moreover, have suggested that, in tissues exhibiting aerobic glycolysis, the lack of rhodanese would permit an accumulation