Influence of copper ions on uterine activity

The influence of copper ions on myometrial activity was tested in nonpregnant rabbits $\text{in vitro}$ and $\text{in vivo}$, and in nonpregnant women $\text{in vivo}$. In an organ bath, CuCl₂ in concentrations of 3 μM and higher caused a dose-dependent increase in the contractile activity of isolated rabbit myometrium. In rabbits $\text{in vivo}$, intrauterine instillations of 0.2 to 2 mM of CuCl₂ in 0.6 ml of saline solution caused a dose-dependent increase of myometrial activity in the uterine horn where it was injected, and the response lasted up to 30 minutes. The activity in the other horn remained unchanged and control injections with saline had no effect. Also, in nonpregnant women, a clear and dose-dependent effect of 1 ml of 0.3 to 3 mM of CuCl₂ dissolved in saline was observed after intrauterine instillation. Saline itself in the same volume had no effect. It is estimated that the intrauterine doses of copper which were used in these experiments lead to Cu⁺⁺ concentrations in the uterine tissues which were similar to those in women carrying a copper IUD, and it is suggested that the copper from such IUDs might have effects on myometrial activity contributing to the contraceptive action and to some of the side-effects of these devices.