Early embryonic development in lead-intoxicated mice.

The development of the embryo until day 7 was studied in histologic sections of the uterus, oviduct, and ovary from normal and lead-treated mice (0.5% of lead in the diet). Such lead treatment causes a substantial reduction in pregnancies in successfully mated female mice. After lead treatment, the blastocyst is formed normally, although it has a slightly reduced size. Differentiation of giant cells in the trophoblast and of decidua cells in the uterus is, however, impaired. Moreover, the corpora lutea are underdeveloped. Since earlier normal estradiol secretion on day 4 and a diminished progesterone secretion from day 5 on had been found, activation of the embryo and/or development of decidua cells fall due to the absence of this hormone.