Restriction of cellular iodide space by mediated efflux

Abstract

• 1.

  1. The movements of I⁻ and other anions in Ehrlich ascites tumor cells were studied as a model to explain the restricted anion space of certain cells.

• 2.

  2. At 38° all the anions tested (I⁻, Br⁻, ReO₄⁻, WO₄²⁻) penetrate only one-quarter of the cell volume. For I⁻ this value, constant up to 6 h, is independent of the anion concentration in the medium from less than 1 μM to 0.124 M and is insensitive to anions that inhibit thyroidal I⁻ transport competitively.

• 3.

  3. At 4° the restriction of the I⁻ (and Br⁻) compartments (but not that of ReO₄⁻ or WO₄²⁻) is abolished and the I⁻ space approaches the water content of the cell. Upon exposure of the cold-loaded cells to 38°, a net efflux of the halide is observed until the steady-state value of one-quarter of the cell volume is again attained.

• 4.

  4. The temperature-dependent efflux of I⁻ is sensitive to various metabolic inhibitors, but, in ascites fluid, at a rather high concentration.

• 5.

  5. Cardiac glycosides and quinidine markedly decrease the ability of ascites cells to restrict the anion space. The same effect is produced by nucleoside triphosphates, particularly ATP, ITP and UTP.

• 6.

  6. The behavior of I⁻ and Na⁺ was compared under identical conditions. Although certain similarities exist, a number of differences were noted.

• 7.

  7. The evidence presented is consistent with the hypothesis that the halide restriction in ascites cells is due to a metabolism-dependent efflux.