PROLACTIN STIMULATION OF IODIDE UPTAKE INTO MOUSE MAMMARY-GLAND EXPLANTS

These studies show that prolactin (PRL) stimulates iodide accumulation in cultured mouse mammary tissues. This effect of PRL likely causes t he elevated concentration of iodide that occurs in the milk of a numbe r of species. In time course studies, an initial effect of PRL occurre d after 4 h, whereas a maximum two- to threefold increase was observed after 24 h. In dose-response studies, 1 ng/ml PRL elicited a signific ant response, whereas PRL concentrations >5 ng/ml stimulated maximum r esponses. Other lactogenic hormones, including human growth hormone (G H) and human placental lactogens, also stimulated iodide uptake, where as nonlactogenic substances, including bovine GH, bovine serum albumin , and thyroid-stimulating hormone, were without effect. PRL had no eff ect on iodide uptake into fat cells. In further studies it was shown t hat PRL stimulates iodide incorporation into macromolecules in a 10% t richloroacetic acid precipitable tissue fraction as well as in a pH 4. 6 isoelectric precipitate. The findings from these studies suggest tha t PRL may stimulate both the accumulation of free iodide in milk and i odide incorporation into milk proteins.