Cultured rat embryo accumulation of DNA, RNA, and protein following maternal administration of sodium arsenate.

Whole embryo culture techniques were used to test the effects of sodium arsenate on the rates of DNA, RNA, and protein accumulation. Rat embryos were isolated on the 10th gestational day (sperm day = Day 0) either 4 or 24 hr after maternal injection. The cultivation period was for 24 or 42 hr. DNA, RNA, and protein values were not significantly different for in utero treatment 4 hr prior to dissection. For embryos treated in utero 24 hr prior to dissection, DNA, RNA, and protein levels were significantly lower at the beginning of cultivation and after 24 hr in culture. By 42 hr, DNA and RNA values were still significantly reduced. A number of morphologic differences were also noted following cultivation for embryos treated in utero 24 hr prior to dissection. These include a significant number of embryos failing to (1) rotate to a ventroflexed position, (2) have a closed anterior neuropore, (3) establish a visceral yolk sac circulation, and (4) fuse the allantoic sac in placental formation. It is concluded that sodium arsenate takes longer than 4 hr to affect the embryo and that a 24-hr in utero exposure is adequate to initiate teratogenic responses. The abnormal persistence of a definitive allantoic sac after culture may be indicative of abnormalities in urogenital system formation. The effects of sodium arsenate seem to be related to proliferative embryonic cell requirements with some insult recovery of the embryo possible.