The Male-Induced Implantation Failure (the Bruce Effect) in Laboratory Mice: Investigations on Luteal Failure in Pregnancy-Blocked Females

Summary

The luteal function in newly inseminated female mice following exposure to alien males was investigated. The corpora lutea (CL) of newly inseminated females exhibited high Δ⁵ 3β hydroxysteroid dehydrogenase (Δ⁵ 3β HSD) activity at 24 hr or 48 hr (pro-oestrus) after the beginning of alien male exposure. By contrast, the enzyme activity in the CL at 72 hr (oestrus) after the beginning of alien male exposure was markedly less as compared with that in the CL of unexposed controls. This suggests that the CL of newly inseminated female mice can synthesise progesterone from its substrate at least up to 48 hr after the beginning of alien male exposure. Administration of pro-lactin to newly inseminated females beginning at 0 hr of alien male exposure prevented implantation failure; the majority of females showed implanted embryos. Prolactin administration starting at 24 hr after the beginning of alien male exposure was only partially effective, and that starting at 48 hr was totally ineffective in preventing implantation failure in newly inseminated females. The results indicate that the CL of newly inseminated females cease to respond to prolactin within 24 hr of alien male exposure, even though they exhibit the capacity to synthesise progesterone (as evidenced by the presence of Δ⁵ 3β HSD activity) for a longer period.

Key words

Bruce effect - Mice - Luteal failure - Corpora lutea - Δ⁵ 3β Hydroxysteroid dehydrogenase - Prolactin