AJP - Endocrinology and Metabolism, Vol 246, Issue 5 436-E443, Copyright © 1984 by American Physiological Society
Distribution of sodium in cellular and luminal compartments of turtle thyroid glands
Y. C. Yen-Chow, S. Y. Chow and D. M. Woodbury
Sodium distribution in luminal and cellular compartments of turtle thyroid
was studied by measurements of radiosodium uptakes into whole thyroid and
luminal fluid, sampled with micropipettes, and of Na+ activities in the
luminal and cellular fluids of thyroid follicles with a liquid ion-exchange
microelectrode. Thyroid water and electrolyte contents were also determined
chemically. Radiosodium uptake by both the whole thyroid and by the luminal
fluid of control and thyrotropin (TSH)-treated turtles did not reach
maximal levels until 16-24h after injection of the radioisotope. In control
animals, the volumes of distribution of radiosodium in the whole thyroid
and the luminal fluid were much smaller than those calculated from the
chemical analysis data for the corresponding tissues. TSH increased the
radiosodium spaces to values almost equal to those of the chemically
determined sodium spaces. Luminal fluid sodium concentration increased
after TSH and decreased after ouabain and furosemide treatments.
Intracellular sodium concentration markedly increased after ouabain and
decreased after TSH and furosemide. These and our previous results suggest
a Na+-I- cotransport mechanism in the thyroid.
