On dense bodies and droplets in the follicular cells of the guinea pig thyroid

Abstract

A large number of dense bodies are found in the follicular cells of nonstimulated as well as TSH-stimulated guinea pig thyroids. Administration of TSH induces the formation of numerous intracellular droplets of various appearances. The dense bodies are often topographically intimately related to the droplets. In tissues incubated for acid phosphatase activity, reaction products are found in the dense bodies and in some droplets. When I 125 is administered several hours and TSH 1 or 2 hours before autopsy autoradiographic reaction is observed over the luminal colloid and over most, but not all, of the droplets. When TSH is given 1 or 2 hours and radioiodide 15 minutes before sacrifice, the luminal colloid is labeled but only an occasional intracellular droplet. The observations seem to corroborate the conclusions reached by previous authors that thyroglobulin is resorbed from the luminal colloid in the form of intracellular droplets and that the thyroglobulin in the droplets is hydrolyzed by enzymes derived from the dense bodies inside the cell. The heterogeneity of the intracellular droplets both with respect to morphology and labeling seem to indicate, however, that some of them represent other processes than thyroglobulin resorption and breakup.