Characteristics of the prolactin stimulation of iodide uptake into mouse mammary gland explants.

We have recently reported that prolactin (PRL) stimulates iodide uptake into cultured mouse mammary tissues. This effect occurs in both TCA soluble and insoluble tissue fractions. The effect of PRL apparently involves an RNA-DNA-dependent mechanism, since actinomycin D and cyclohexamide abolish the PRL stimulation of iodide uptake and its incorporation into protein. Perchlorate and thiocyanate, inhibitors of the iodide transporter, also abolish the PRL effects on iodide uptake and incorporation. Similarly, propylthiouracil and aminotriazole, inhibitors of peroxidase, abolish both effects of PRL. Finally, the extent of iodide uptake in mammary cells is suppressed by about 50% in sodium-free medium. These studies thus suggest the existence of a sodium-iodide symporter in the mammary gland which has characteristics similar to the iodide transporter in the thyroid gland-that is, it is sodium dependent and is inhibited by perchlorate and thiocyanate. The fact that both iodide transporter inhibitors and peroxidase inhibitors abolish PRL-stimulated iodide uptake and incorporation suggests that there may be a coupled mechanism involving the iodide transporter and the peroxidase enzyme.