[Mechanisms of the negative effect of blood serum on iodine-131 uptake by cultured thyrocytes].

Embryonal (calf) and ordinary (cattle) blood sera have ben studied experimentally on a primary culture of thyroid cells from newborn pigs for their effect on basal and thyrotropin (TSH)-stimulated 131I uptake by thyrocytes. It is shown that the value of this index is inversely proportional to the relative percentage of the blood serum in the cultivation medium. The concentrations being equal, the ordinary blood serum effect is more pronounced than the embryonic one. Thyrocyte incubation in a medium with 1% blood serum and 0.1-10.0 mU/ml TSH stimulates 131I uptake by the cells, whereas 15% concentration of the blood serum blocks the influence of this hormone. Ouabain (0.1 mM) and cyclohexamide (10 micrograms/ml) have also an inhibiting effect on exposure of the basal and TSH-stimulated uptake of the isotope. It is suggested that the blood serum contains biologically active substances inhibiting the transmembranous transfer of iodides into thyrocytes. This process is controlled by Na+, K(+)-ATPase, and its TSH-stimulation is mediated by protein synthesis de novo.