Tissue peroxidase in the normal and neoplastic salivary gland

Peroxidase activity was measured by two colorimetric methods in six neoplastic tumors of the parotid salivary gland. When p-phenylenediamine was used as the hydrogen donor co-substrate, peroxidase activity was absent or reduced from 6 to 22% of normal in these tumors. Cross reactivity with normal peroxidase antibody could not be demonstrated in tumors exhibiting negative activity. Two neoplastic salivary glands had well-described, encapsulated tumors which showed reduced peroxidase activity when compared with the normal uninvolved portion. However, when guaiacol was substituted for p-phenylenediamine, normal activity was recorded. After dialysis, peroxidase activity was not enhanced. Mixing experiments showed no effect of the tumor extract on the peroxidase activity of normal saliva, nor on salivary gland supernatant. Normal salivary gland peroxidase was inhibited 90% by 10(-2) g/L amino-triazole, but neoplastic tumors were inhibited less (13 and 73%). It is suggested that peroxidase is a simple marker for the detection of neoplasia and can be of value in the differentiation of benign tumors.