title: Iodide transport of thyroid plasma membranes.
abstract: Plasma membranes consisting of closed vesicles were isolated from hog thyroid homogenate. The membrane vesicles showed uphill transport of iodide from an external medium containing monovalent cations, of which K+ induced iodide transport more potently than Na+. The activity of the iodide transport expressed as T/M[I-] was as little as 3 to 11 in the presence of K+, but was invariably present. The ratio reached a maximum within about 10 min and then decreased fairly rapidly to unity. The addition of SCN- or CIO-4 to the external medium inhibited iodide transport. The transport activity was found to be maximum at pH 7.0 to 7.5 in the external medium. A kinetic study showed that the transport rate was saturated with respect to the iodide concentration. These observations suggested the presence of a carrier-mediated iodide transport system which was coupled with K+ flux across the plasma membrane.
mesh_terms: D000818:Animals; D001693:Biological Transport, Active; D002462:Cell Membrane / Q000378:metabolism*; D002499:Centrifugation, Density Gradient; D007454:Iodides / Q000378:metabolism*; D008854:Microscopy, Electron; D011189:Potassium Chloride / Q000494:pharmacology; D012965:Sodium Chloride / Q000494:pharmacology; D013552:Swine; D013961:Thyroid Gland / Q000378:metabolism*
chemical_list: D007454:Iodides; D012965:Sodium Chloride; D011189:Potassium Chloride