Viability of the Rat Blastocyst Following the Oral Administration of Potassium Perchlorate or Potassium Iodide to the Mother

During a limited period (Day 3 to Day 5) of early pregnancy the epithelial cells of the endometrium of the rat develop the ability to accumulate inorganic iodide from the blood and to maintain a very high intracellular concentration of this ion (Brown-Grant, 1965; Brown-Grant & Rogers, 1967). These changes occur just before the normal time of blastocyst implantation but their physiological significance in normal pregnancy is not known. If endometrial accumulation of iodide is prevented by the oral administration of perchlorate to the mother, pregnancy still proceeds normally (Brown-Grant, 1966a). When implantation is delayed by ovariectomy early in pregnancy followed by the administration of progesterone alone or by concurrent lactation, the changes in endometrial iodide concentration still occur but are not immediately followed by implantation (Brown-Grant, 1966b). The