Origin of intracellular colloid droplets in the rat thyroid.

Abstract

After a single injection of thyroid- stimulating hormone (TSH) to rats, discrete droplets, which stain like the colloid in the lumen, were located in one or more of 3 sites: 1) within streamers of cytoplasm extending into the lumen from the apex of the follicular cells, 2) within the body of the cells either toward the apex or 3) toward the base. In a first experiment, counts of colloid droplets in these 3 locations after TSH injection indicated that they appear first in the cell streamers, later in the apex, and finally in the base of the cells. In a second experiment, colloid droplets were produced again by TSH, but in animals given leucine-H3 either ½ hour before sacrifice (when radioautography showed labeling solely of follicular cells) or 5 ½ hours before sacrifice (when labeling predominated in the luminal colloid). Only in the latter case was there any significant labeling of the colloid droplets. The interpretation was that the droplets originate from the luminal colloid—a conclusion in keeping wi...