UTERINE UPTAKE OF [6,7-3H] OESTRADIOL IN THE PRESENCE OF INTRAUTERINE CONTRACEPTIVE DEVICE IN CYCLIC AND PREGNANT RATS

Abstract

Uterine uptake of tritiated oestradiol was studied on each of the 4 days of the oestrous cycle and of the first 5 days of pregnancy in rats fitted unilaterally with an intrauterine contraceptive device (IUD). The uptake (dpm/g wet weight) was maximal in the control horn on Day 3 of the cycle and pregnancy. On an average the IUD-bearing horn accumulated more radioactivity than the control horn both during the cycle and pregnancy. It is postulated that the IUD either induces formation of or activates the uterine receptors which specifically bind oestrogen, resulting in an increased exposure of the IUD-bearing horn to endogenous oestrogen. A possible relevance of this finding to the contraceptive effects of the device through the mediation of prostaglandin release is discussed.