The effects of low dose diethylstilbestrol administration in neonatal female rats

Abstract

Two groups of ten female rats were injected with 0.5 μg or 1.0 μg diethylstilbestrol (DES) on day 5 or days 5 and 6, respectively. Other groups were injected with 100 μg testosterone propionate (TP) on day 5 or day 6, respectively. One group was kept as uninjected controls. Body weights were the same for all groups even though the treated animals showed precocious vaginal opening. Animals treated on day 5 with TP showed a greater precocity than those treated on day 6. In another experiment, groups of ten rats were treated on day 3 with 30 μg TP, 5.0 μg estradiol benzoate (EB), 0.5 (DES) and sesame oil. All but the oil injected animals showed persistent vaginal estrus. DES and EB treated rats showed an increase in the percentage of persistent estrus with increasing age. The ability of very low doses of DES to sterilize female rats is consistent with observations of a specific estrogen binding protein which is present in the blood of newborn female rats and does not appear to bind non-estrogen steroids, and thus would not block masculinization by DES or TP.