Hyperosmotic effects on the cat thyroid perfused in vitro

¹ Department of Research Physiology, William H. Singer Memorial Research Laboratory, Allegheny General Hospital, Pittsburgh, Pennsylvania

Tissue blocks containing the thyroid gland of cats were perfused via the carotid artery with normal and hypertonic defibrinated bovine whole blood for 2-hour intervals. Details of apparatus and methods for in vitro perfusion are described. Hypertonic perfusion resulted in reduced Na²⁴ and I¹³¹ passage into the gland. The rate of in vivo accumulated I¹³¹ (inorganic and organic) movement from the gland to the hypertonic perfusate was increased. Tissue sodium and potassium was increased on a dry weight basis and a thyroid weight loss was observed due to loss of water to the hypertonic perfusate. Radiochromatograms of hypertonically perfused glands showed markedly reduced total I¹³¹ and synthesis of diiodotyrosine and monoiodotyrosine. It was concluded the thyroid responded to movements of iodide into and out of the cells in a manner that reflected the osmotic state of the external environment.