The effect of a copper intrauterine device on the uterine histology and progestational response in pregnant and immature rabbits.

A copper wire intrauterine device (GuIUD) was inserted into mature female rabbits 14 days prior to artificial insemination (AI), and its effect on the histology of the pregnant uterus was studied 48 to 192 hours after AI. In a related study, estrogen-primed immature femal rabbits were fitted with a device consisting of 321 mm of copper wire wound around a 17-mm plastic carrier and treated subcutaneously for 5 days with 0.1 mg of progesterone daily. Uterine tissue samples were obtained on the following day, examined histologically, and tested for carbonic anhydrase activity. In both studies, gold wire devices, similar to the respective copper devices, and sham surgery served as controls. In the pregnant rabbit, the McPhail score (McPhail MK: J Physiol (Lond) 83:145, 1934) measuring arborization of the luminal epithelium was significantly lower in tissue surrounding the CuIUD than in tissue anterior to the CuIUD or in tissue from the contralateral control horn bearing an AuIUD or subjected to sham surgery, 96 to 192 hours after AI. The morphologic development of the epithelial cell structure was retarded only in areas surrounding the CuIUD 96 to 192 hours after AI. There were no observable differences in the stroma or in the leukocytic infiltration of the tissue. In the estrogen-primed immature rabbits, the ability of the tissue to react to exogenous progesterone was depressed in tissue surrounding the copper device, as determined by the lower McPhail score, compared with tissue anterior to the copper device or from contralateral controls. Similary, progestational stimulation of carbonic anhydrase was blocked significantly in tissue surrounding the CuIUD and, to a lesser extent, in tissue anterior to the CuIUD. The data suggest that copper ions eluted from the CuIUD produce a contraceptive effect by locally blocking the action of progesterone on the epithelial tissue.