Inhibitory Effect of an Ultracentrifugal Fraction of Rat Renal Homogenate on TSH-Stimulated 131 I Uptake by Bovine Thyroid Slices 1

Abstract

Summary

The kidneys of rats contain a factor, extractable in normal saline, which depresses the uptake of ¹³¹I by slices of bovine thyroid gland in vitro. The thyroid depressing factor (TDF) is present in ultraeentrifugal fractions of kidney (35.000g for 0.5 hour) and inhibits the stimulatory effect of TSH on ¹³¹I uptake. Thus, a graded increase in concentration of renal factor in the incubation medium resulted in a graded depression in ¹³¹I uptake by bovine thyroid slices stimulated to take up iodide by TSH (100 mU/ml medium). An experiment designed statistically to reveal interaction between TSH and TDF failed to demonstrate significant interaction. The exact mechanism by which TDF blocks the stimulatory effect of TSH on iodide uptake cannot be ascertained from these studies but the results suggest that TDF inhibits some aspect of iodide transport and thereby prevents TSH from manifesting its typical effect.