Some biochemical and cytogenetic properties of rat thyroid tumors.

the host thyroid. The tumors themselves showed extremely low incorporation, although thyroidectomy of the host significantly increased the incorporation in the tumors. However, results of incorporation experiments do not distinguish the transitional from the autonomous tumors. Tumor growth also caused iodide peroxidase activity in the host thyroid to decline. The enzyme activity in the transitional tumor approached the activity in normal thyroid. Thyroidectomy of the host, however, greatly reduced the enzyme activity in the tumor. By contrast, the autonomous tumor had no measurable peroxidase activity. Apparently, no correlation exists between the incorporation and the enzyme activity in the tumor, although both biochemical parameters are subject to the influence of the host thyroid. However, the results indicate that iodide peroxidase activity can serve as a more sensitive gauge to measure the progression of the thyroid tumor from a transitional to an autonomous stage than can 13 ' I incorporation.