Accumulation of Amino Acids by Thyroid Gland Slices

The kinetics of amino acid uptake by bovine and dog thyroid gland slices has been studied employing the model amino acids α- aminoisobutyric acid (AIB) and cycloleucine, as well as glycine, L-histidine, L-tyrosine and Lvaline. Of the model compounds only cycloleucine accumulation resembled that of the naturally occurring amino acids. Alpha-aminoisobutyric acid continued a linear uptake curve for 4 hr of incubation, in marked contrast to the other amino acids, which reach steady-state levels in tissue after 30 min. The data indicate cycloleucine to be the best model amino acid for study of transport in thyroid tissue. TSH caused a statistically significant small increase in AIB uptake but no effect was observed with other amino acids studied.(Endocrinology79: 675, 1966)