Extrathyroidal Iodide Pump in Tadpoles (Rana grylio).

Large amounts of iodide are accumulated in the gastrointestinal tract of tadpoles despite the presence of ligatures on the bile duct or esophagus or on both structures. These ligatures exclude the possibility that the iodine-131 tracer reaches the gastrointestinal tract by way of the bile or esophagus. The iodide in the gastrointestinal tract localizes largely in the stomach. The stomach therefore acts as an iodide pump and may be responsible for the maintenance of the iodide levels that are needed in metamorphosis.