Administration of minute quantities of 17 beta-estradiol on the nasal areaterminates early pregnancy in inseminated female mice

It is well established that chemical emissions of novel males disrupt intra uterine implantation of fertilized ova in inseminated female mice, but the specific nature of these chemicals is not known. Given that novel males exc rete androgens and estrogens in their urine and feces, the current experime nts were designed to determine whether nasal application of these steroids could disrupt pregnancy, Nasal application of testosterone propionate to fe males during early pregnancy had no impact on gestation. However, nasal app lication of 17 beta -estradiol terminated all pregnancies in females at all doses greater than or equal to approximately 1 mug/day. Nasal application of 17 beta -estradiol benzoate similarly terminated all pregnancies in fema les at very low doses. In subcutaneous administration, 17 beta -estradiol i s also the most potent steroid in disrupting pregnancy compared to other es trogens and androgens. These data suggest the possibility that males' emiss ion of estrogens is among factors mediating the Bruce effect. (C) 2001 Else vier Science Inc. All rights reserved.