Thyrotropin Stimulation of32P Incorporation into the Phospholipids of Canine Thyroid Adenocarcinoma

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Abstract
Six carcinomas of the canine thyroid were studied. Five of the 6 tumors were functional on 131I scan and caused hyperthyroidism in 2 cases. The tumors were all of predominantly compact cellular histology with rare to moderate numbers of microfollicles. After surgical removal tumor slices were incubated with 32P in Krebs-Ringer-tris buffer with or without 0.1 U/ml of bovine TSH [thyrotropin], and the specific activity of the extracted phospholipids was measured. TSH stimulated phosphatide turnover in 5 cases and probably also in the 6th. Analysis of fractionated phospholipids in 2 cases showed that the response to TSH was in the phosphatidic acid and phosphatidylinositol. These studies show that malignant tumor may still retain at least 1 complete control system extending from TSH receptors to the final metabolic response.