The Effect of LATS and TSH on Protein and RNA Synthesis in Isolated Thyroid Cells 1

Abstract

Summary

The effects of Long-Acting Thyroid Stimulator (LATS) and of pituitary thyrotropin on macromolecular biosynthesis by isolated thyroid cells were measured. LATS consistently produced up to 3-fold stimulation of the incorporation of protein and RNA precursors by such thyroid cells. The stimulation was linear with time. TSH under similar conditions, on the other hand, did not exert any significant stimulation of the uptake of labeled leucine or uridine by the thyroid cells. In the presence of cyclic AMP, however, TSH stimulated the uptake of leucine up to 36% and that of uridine up to 80%. Actinomycin D at a concentration of 20 μg/ml inhibited, by 70%, the stimulatory effect of LATS on both RNA and protein synthesis. The antibiotic effect indicates that the stimulation of LATS of protein synthesis is dependent upon new RNA synthesis. The data suggest that the kinetics of the binding of LATS and of TSH to thyroid cells, as demonstrated by their subsequent effects on subcellular macromolecular synthesis, are not identical, but does not indicate whether their mechanism of action are different.