CORRELATION OF WATER AND ELECTROLYTE DISTRIBUTION IN THE THYROID GLAND WITH ITS FUNCTIONAL STATE IN RATS AND GUINEA-PIGS

Abstract

In the thyroid gland of rats and guinea-pigs, follicular cell fluid volume was increased and luminal fluid volume was decreased after a single injection of thyroid-stimulating hormone (TSH) (1 i.u./animal) or long-term administration of propylthiouracil (PTU) (0·1% in drinking water for 2 weeks). In rats, follicular cell fluid volume was decreased and luminal fluid volume was increased after hypophysectomy. Interstitial fluid volume remained fairly constant in different functional states of the thyroid gland in both species. As a result of the decrease in luminal colloid content by TSH and PTU treatments, the Cl⁻ concentration in the luminal compartment of the thyroid gland was increased. Luminal Cl⁻ concentration decreased in hypophysectomized rats. In the cellular compartment of the thyroid gland, TSH and PTU treatments caused an increase in K⁺ and Cl⁻ concentrations and a decrease in Na⁺ concentration, whereas hypophysectomy caused a decrease in K⁺ and Cl⁻ and an increase in Na⁺ concentrations. Water and electrolytes in the thyroid gland of rats younger than 5 weeks were distributed in the same pattern as that of adult guinea-pigs and hypophysectomized adult rats; all these animals probably had lower TSH activity than intact adult rats.