Novel mates' capacity to disrupt early pregnancy in mice (Mus musculus) is attenuated via a chronic reduction of males' urinary 17β-estradiol

Mature mate mice of proven fertility were administered chronic oral doses of anastrozole, a potent aromatase inhibitor, and also given a low-phytoestrogen diet. Urine was taken non-invasively from such mates and from untreated control mates and assayed for 17 beta-estradiol and testosterone via ELISA procedures. After 8 weeks of drug or vehicle administration, urinary 17 beta-estradiol declined to significantly lower levels in anastrozole-treated mates than in nontreated mates, whereas testosterone levels were comparable in the two groups. Inseminated females were exposed to drug-treated, vehicle-treated, or no mates during days 1-6 of gestation, around intrauterine implantation of fertilized ova. Females exposed to vehicle-treated mates produced fewer litters than did those kept in isolation. Females exposed to anastrozole-treated mates produced significantly more litters than did those exposed to vehicle-treated mates. These data support the notion that mate excretions of estrogens may in part mediate novel-mate-induced pregnancy disruptions, although other influences of aromatization on behaviour and metabolism remain possibilities. (c) 2005 Elsevier Ltd. All rights reserved.