THE SPONTANEOUS FORMATION OF INTRACELLULAR COLLOID DROPLETS IN SURVIVING CHICK THYROID TISSUE1

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Abstract
Entire thyroids of young cockerels were incubated in a variety of media for 1-8 hrs. at from 5[degree]C to 43[degree]C under different gases in media to which 0.01 [image] to 0.0001 [image] thyroxine, Nal, I2, thiouracil, thyrotrophic hormone, NaCN, NaF, KSCN, or KMnO4 were added. The effect of progressive ischemia on thyroids of intact chicks was studied. Thyroids were fixed in Carnoy''s fluid, and stained to demonstrate colloid. Numerous large intracellular colloid droplets formed and colloid loss occurred, in vitro, in the centers of most thyroids, without added thyrotrophic hormone. After 8 hrs., the centers became partly necrotic. These responses depended on the inner position of the follicles, since they did not occur in the periphery. Colloid depletion occurred in peripheral follicles when thyroids were incubated in I2, NaCN, or H2O. These responses were prevented by incubation at low temp., or by incubation in strongly acid or basic or hypertonic media. Incubation in distilled water resulted in colloid depletion throughout the gland, while incubation in solns. containing elemental I allowed colloid depletion in the peripheral follicles. Both prevented colloid droplet formation. Other agents did not stop the reaction, though they may not have diffused into the centers of the glands. Thyrotrophic hormone stimulated formation of small colloid droplets in peripheral thyroid follicles, a zone usually lacking them. Only completely ischemic thyroids formed intracellular colloid droplets in living chicks. Fewer droplets formed when the thyroids remained undisturbed in decapitated chicks.