The Significance of Indole-3-Acetic Acid in Tumor-Bearing Rats

Abstract

Indoleacetic acid (IAA) acts as a regulating factor of cell division not only on plant cells but also on animal cells. We report here the significance of IAA in tumor-bearing rats, of which sarcomas were induced by subcutaneous injection of 20-methylcholanthrane to Wister rats. When enlarged by several cm³, most of the tumor tissues possessed a higher concentration of IAA than that of non-neoplastic tissues, while tumor tissues under 1 cm³ in size contained no or negligible contents of IAA. Mitotic indices were significantly higher in tumors with a high concentration of IAA than in tumors containing no or negligible contents of IAA. Considering these findings, it is inferred that endogenous IAA in the tumor acted on itself to increase the proliferation rate. Although no definite relation between tumor cell differentiation and IAA concentration was recognized, a relatively well differentiated tumor tissue containing no IAA in spite of its large size was noted. Necrosis in the tumor tissue did not influence IAA concentration. IAA concentration in serum did not increase in the tumor-bearing rats.