Chloride channel blockers inhibit the Na+/I- symporter in thyroid follicles in culture.

Porcine thyroid cells in culture are able to reorganize into well-polarized follicle-like structures in the presence of cAMP analogs. These follicles exhibit on their basolateral membrane domain the Na+/I- symporter which allows iodide to accumulate in the thyrocytes. The initial rate of iodide influx through the Na+/I- symporter is inhibited up to 98% by the chloride channel blockers. 5 nitro-2(3-phenylpropylamino)benzoic acid and 3',5-Dichlorodiphenylamine-2-carboxylic acid are the most effective inhibitors, with a K0.5 value of 60 microM. This inhibition is not secondary to inhibition of chloride transport. Other chloride transporter blockers have been studied but showed lesser activities.