Electrochemical effects of metals on IUDs.

Electrochemical effects within the uterus are being studied, particularly as they pertain to IUDs made in total or in part of metals. The intrauterine potential as measured with either metal or nonpolarizable salt electrodes is positive at the fundal with respect to the cervical end of the uterus. Placement of dissimilar metal electrodes within the uterus will induce voltage gradients that are roughly predictable from their cell potential in blood as an electrolyte. When copper and zinc electrodes are placed at opposite ends of the uterus, they induce voltage gradients that are typically greater than 100 mv per cm. External copper and zinc wires connected at one end, and with the other ends in contact with various positions on the skin of rats, were found to influence potential gradients within the uterus. When a length of zinc wire was wound around the upper portion of the stem of a small Cu-7 200 IUD, it took about 1 year from insertion for the zinc to disappear. When the zinc wire was wound around the lower portion of the stem, it disappeared in 1 month. The zinc reduced intrauterine corrosion of the copper and it was more effective at reducing copper corrosion when in the lower stem position.