Effect of copper intrauterine devices (IUD's) on estrogen and progesterone uptake by the rat uterus

Abstract

The uptake of labeled estrogen and progesterone by the uterus of spayed rats fitted with inert (nylon) and active (copper) IUD's in the right horn was studied in vivo. Progesterone uptake was determined both in animals primed and nonprimed with estrogen. Inert IUD's did not modify estrogen uptake, while active IUD's increased it, but only in the treated horn. Progesterone uptake was not modified by any of the IUD's used, regardless of whether the rats had been primed with estrogen uptake remains to be determined. Since copper did not increase progesterone uptake in spite of the fact that it increases estrogen uptake it cannot be considered an estrogen. The results demonstrate that active IUD's apparently have mechanism(s) of action different from inert IUD's.