Excretion and binding of tritium-labelled oestradiol in mice (Mus musculus): implications for the Bruce effect

Male mouse urine contains 17β-oestradiol (E2) and other steroids. Given that males actively direct urine at proximate females and intrauterine implantation of blastocysts is vulnerable to minute amounts of exogenous oestrogens, males' capacity to disrupt early pregnancy could be mediated by steroids in their urine. When male mice were implanted with osmotic pumps containing tritium-labelled E2(3H-E2) or injected i.p. with3H-E2, radioactivity was reliably detected in their urine. Following intranasal administration of3H-E2to inseminated females, radioactivity was detected in diverse tissue samples, with there being significantly more in reproductive tissues than in brain tissues. When urine was taken from males injected with3H-E2, and then intranasally administered to inseminated females, radioactivity was detected in the uterus, olfactory bulbs, and mesencephalon and diencephalon (MC+DC). When inseminated and ovariectomised females were perfused at the point of killing to remove blood from tissues, more radioactivity was detected in the uterus than in muscle, olfactory bulbs, MC+DC and cerebral cortex. Pre-treatment with unlabelled E2significantly reduced the uptake of3H-E2in the uterus. Taken with evidence that males deliver their urine to the nasal area of females, these results indicate that male urinary E2arrives in tissues, including the uterus, where it could lead to the disruption of blastocyst implantation.

Excretion and binding of tritium-labelled oestradiol in mice (Mus musculus): implications for the Bruce effect Journal Articles