AbstractsBiology & Animal Science

An electron microscopic study of colloid droplets and dense bodies in the thyroid follicular cells of TSH-injected and non-TSH-injected rats indicated the following: 1) Colloid droplets and dense granules were situated on the average slightly nearer to the apex of the cell than to the base. On the average, one micron separated a colloid droplet from the nearest dense body. TSH did not significantly affect these values. 2) Colloid droplets varied in density between gray and white. The lighter droplets showed matrix filaments of a size similar to reported dimensions of thyroglobulin crystals. Density variation may represent stages of thyroglobulin digestion. 3) The relative infrequency and non-specificity of close association of dense bodies with colloid droplets, and the absence of electron density changes in colloid near dense bodies, suggest there is possibly only a minor contribution by dense bodies of enzymes for colloid droplet degradation.