Affinity of many inorganic compounds for the malignant
tumor was examined, using the rats which were subcutaneously transplanted with
Yoshida sarcoma. And the relations between the uptake rate into the malignant
tumor and in vitro binding power to the
protein were investigated in these compounds. In these experiments, the bipositive
ions and
anions had not affinity for the
tumor tissue with a few exceptions. On the other hand, Hg, Au and Bi, which have strong binding power to the
protein, showed high uptake rate into the malignant
tumor. As Hg++, Au+ and Bi+++ are soft
acids according to classification of
Lewis acids, it was thought that these elements would bind strongly to soft base (R-SH, R-S-) present in the
tumor tissue. In many hard
acids (according to classification of
Lewis acids), the uptake rate into the
tumor was shown as a function of ionic potentials (valency/ionic radii) of the
metal ions. It is presumed that the chemical bond of these hard
acids in the
tumor tissue is ionic bond to hard base (R-COO-, R-PO3(2-), R-SO3-, R-NH2).