LOCALIZATION OF ETHYNYLOESTRADIOL IN THE REPRODUCTIVE TRACT OF WOMEN

Abstract

SUMMARY [4-14C]Ethynyloestradiol was administered to women at varying times before hysterectomy. At operation, samples of blood, adipose tissue and tissue from the reproductive tract were obtained. All tissues examined took up radioactivity, the concentration at 1 h varying from 0·22 to 0·4% of the dose per 100 g of tissue except for stroma and endometrium which showed high levels (0·68% and 0·60%, respectively). By 24 h the amount of radioactivity in the tissues had decreased markedly. Mean values for the amount of radioactivity present in total tissues at 1 h were: uterus, 0·9%; adipose tissue, 28·2%; blood, 8·8%. By 24 h these values had declined to 0·2%, 6·8% and 1·6%, respectively. In adipose tissue almost all the radioactivity was present in a freely extractable state whereas in myometrium and cervix about 20% of the radioactivity was in a conjugated form. In plasma, more than 80% of the metabolites were conjugated, mainly as sulphates. The major metabolite detected in the uterus was ethynyloestradiol itself and most of the radioactivity in the myometrium was associated with the nuclear fraction. In one pregnant subject studied, radioactivity crossed the placenta and small amounts of the dose were found in the foetus.