THE EFFECTS OF DITHIOTHREITOL ON THYROID STIMULATION IN VITRO

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Abstract
There is evidence that the porcine TSH receptor contains essential disulphide bridge(s) which can be disrupted by dithiothreitol (DTT). The aim of the present study was to determine whether exposure of intact thyroid cells to DTT leads to altered thyroid stimulation. TSH-stimulated iodine organification in cultured porcine thyroid cells was studied following short-term DTT exposure; a dose-dependent inhibition was observed with DTT but not oxidized DTT. Cell viability, follicle formation, and total protein synthesis were preserved. A minimum of 30 min incubation with DTT was required for inhibition. However, under identical conditions, DTT had no effect on TSH or forskolin-stimulated cyclic AMP (cAMP) production. These results suggest that DTT inhibition of organification is mediated by post-receptor mechanisms likely involving thyroid peroxidase. The effects of DTT on thyroid stimulation in vitro does not appear to involve disruption of the disulphide bridge(s) in the TSH receptor.